I have 2014 iMac 5K that doesn't properly fall asleep when idle. The screen turns off, but nothing else does. Backups continue. External harddrives are constantly being accessed (for what, I have no idea). System sounds play. There doesn't even seem to be a settings option to do it. There is an option to "Prevent Computer from sleeping when display is off" which I have unchecked, but there is no "Put the computer the sleep after this amount of time" option like a laptop. Desktops need energy saving too. If this can't be done in system settings is there an app that will properly sleep the machine after so many minutes? Thanks!