diff --git a/knots/resource-pool.scm b/knots/resource-pool.scm
index d802260..301abbd 100644
--- a/knots/resource-pool.scm
+++ b/knots/resource-pool.scm
@@ -749,6 +749,7 @@
     (let loop ((resources '())
                (available '())
                (waiters (make-q))
+               (resources-checkout-count '())
                (resources-last-used '()))
 
       (match (get-message channel)
@@ -762,11 +763,13 @@
                      (loop (cons resource resources)
                            available
                            waiters
+                           (cons 0 resources-checkout-count)
                            (cons (get-internal-real-time)
                                  resources-last-used)))
                    (loop resources
                          available
                          waiters
+                         resources-checkout-count
                          resources-last-used)))
 
              (let ((current-internal-time
@@ -777,6 +780,7 @@
                     (loop (cons resource resources)
                           (cons resource available)
                           waiters
+                          (cons 0 resources-checkout-count)
                           (cons current-internal-time
                                 resources-last-used)))
                    ((reply . timeout)
@@ -800,6 +804,7 @@
                     (loop (cons resource resources)
                           available
                           waiters
+                          (cons 1 resources-checkout-count)
                           (cons current-internal-time
                                 resources-last-used))))))))
 
@@ -836,10 +841,12 @@
                        (loop resources
                              available
                              waiters
+                             resources-checkout-count
                              resources-last-used))
                      (loop resources
                            available
                            (enq! waiters (cons reply timeout-time))
+                           resources-checkout-count
                            resources-last-used))))
 
              (if timeout-time
@@ -862,10 +869,21 @@
                          (loop resources
                                (cdr available)
                                waiters
+                               (let ((resource-index
+                                      (list-index (lambda (x)
+                                                    (eq? x (car available)))
+                                                  resources)))
+                                 (list-set! resources-checkout-count
+                                            resource-index
+                                            (+ 1 (list-ref
+                                                  resources-checkout-count
+                                                  resource-index)))
+                                 resources-checkout-count)
                                resources-last-used))
                        (loop resources
                              available
                              waiters
+                             resources-checkout-count
                              resources-last-used)))
                  (begin
                    (put-message reply (cons 'success
@@ -874,6 +892,16 @@
                    (loop resources
                          (cdr available)
                          waiters
+                         (let ((resource-index
+                                (list-index (lambda (x)
+                                              (eq? x (car available)))
+                                            resources)))
+                           (list-set! resources-checkout-count
+                                      resource-index
+                                      (+ 1 (list-ref
+                                            resources-checkout-count
+                                            resource-index)))
+                           resources-checkout-count)
                          resources-last-used)))))
 
         (((and (or 'return
@@ -892,46 +920,77 @@
                 (list-index (lambda (x)
                               (eq? x resource))
                             resources)))
-           (let waiter-loop ((waiter (safe-deq waiters)))
-             (match waiter
-               (#f
-                (loop resources
-                      (cons resource available)
-                      waiters
-                      (begin
-                        (when (eq? return-type 'return)
-                          (list-set!
-                           resources-last-used
-                           resource-index
-                           current-internal-time))
-                        resources-last-used)))
-               ((reply . timeout)
-                (if (and timeout
-                         (< timeout current-internal-time))
-                    (waiter-loop (safe-deq waiters))
-                    (if timeout
-                        (let ((reply-timeout
-                               (/ (- timeout
-                                     current-internal-time)
-                                  internal-time-units-per-second)))
-                          ;; Don't sleep in this fiber, so spawn a
-                          ;; new fiber to handle handing over the
-                          ;; resource, and returning it if there's
-                          ;; a timeout
-                          (spawn-fiber-for-checkout reply
-                                                    reply-timeout
-                                                    resource))
-                        (put-message reply (cons 'success
-                                                 resource))))
-                (loop resources
-                      available
-                      waiters
-                      (begin
-                        (list-set!
-                         resources-last-used
-                         resource-index
-                         current-internal-time)
-                        resources-last-used)))))))
+           (if (and lifetime
+                    (>= (list-ref resources-checkout-count
+                                  resource-index)
+                        lifetime))
+               (begin
+                 (spawn-fiber-to-destroy-resource resource)
+                 (loop resources
+                       available
+                       waiters
+                       resources-checkout-count
+                       resources-last-used))
+               (let waiter-loop ((waiter (safe-deq waiters)))
+                 (match waiter
+                   (#f
+                    (loop resources
+                          (cons resource available)
+                          waiters
+                          (if (eq? 'return-failed-checkout
+                                   return-type)
+                              (begin
+                                (list-set! resources-checkout-count
+                                           resource-index
+                                           (- (list-ref resources-checkout-count
+                                                        resource-index)
+                                              1))
+                                resources-checkout-count)
+                              resources-checkout-count)
+                          (begin
+                            (when (eq? return-type 'return)
+                              (list-set!
+                               resources-last-used
+                               resource-index
+                               current-internal-time))
+                            resources-last-used)))
+                   ((reply . timeout)
+                    (if (and timeout
+                             (< timeout current-internal-time))
+                        (waiter-loop (safe-deq waiters))
+                        (if timeout
+                            (let ((reply-timeout
+                                   (/ (- timeout
+                                         current-internal-time)
+                                      internal-time-units-per-second)))
+                              ;; Don't sleep in this fiber, so spawn a
+                              ;; new fiber to handle handing over the
+                              ;; resource, and returning it if there's
+                              ;; a timeout
+                              (spawn-fiber-for-checkout reply
+                                                        reply-timeout
+                                                        resource))
+                            (put-message reply (cons 'success
+                                                     resource))))
+                    (loop resources
+                          available
+                          waiters
+                          (if (eq? 'return-failed-checkout
+                                   return-type)
+                              (begin
+                                (list-set! resources-checkout-count
+                                           resource-index
+                                           (- (list-ref resources-checkout-count
+                                                        resource-index)
+                                              1))
+                                resources-checkout-count)
+                              resources-checkout-count)
+                          (begin
+                            (list-set!
+                             resources-last-used
+                             resource-index
+                             current-internal-time)
+                            resources-last-used))))))))
 
         (('remove resource)
          (let ((index
@@ -954,6 +1013,9 @@
                        resources))
                  available   ; resource shouldn't be in this list
                  waiters
+                 (remove-at-index!
+                  resources-checkout-count
+                  index)
                  (remove-at-index!
                   resources-last-used
                   index))))
@@ -964,6 +1026,7 @@
          (loop resources
                available
                waiters
+               resources-checkout-count
                resources-last-used))
 
         (('list-resources reply)
@@ -974,6 +1037,7 @@
          (loop resources
                available
                waiters
+               resources-checkout-count
                resources-last-used))
 
         (('stats reply timeout-time)
@@ -981,6 +1045,7 @@
                 `((resources              . ,(length resources))
                   (available              . ,(length available))
                   (waiters                . ,(q-length waiters))
+                  (resources-checkout-count . ,resources-checkout-count)
                   (checkout-failure-count . ,checkout-failure-count))))
 
            (spawn-fiber
@@ -1000,6 +1065,7 @@
          (loop resources
                available
                waiters
+               resources-checkout-count
                resources-last-used))
 
         (('check-for-idle-resources)
@@ -1040,6 +1106,7 @@
              (loop resources
                    (lset-difference eq? available resources-to-destroy)
                    waiters
+                   resources-checkout-count
                    resources-last-used))))
 
         (('destroy)
@@ -1103,6 +1170,7 @@
          (loop resources
                available
                waiters
+               resources-checkout-count
                resources-last-used)))))
 
   (spawn-fiber