+Expiration works by placing the item into a delete queue, which means that
+it won't possible to retrieve it by the "get" command, but "add" and
+"replace" command with this key will also fail (the "set" command will
+succeed, however). After the time passes, the item is finally deleted from server memory.
+
+Please note the the Danga memcached server removed support for expiration in
+the 1.4 version.
+