SleepLess 2.9

Stop your Mac from going into sleep mode if you haven't used it after a certain period of time, without altering system settings. Disable the sleep mode while keeping the lid of your laptop closed and preventing wasting CPU time. Optionally, deactivate a schedule.

SleepLess is a utility that prevents the computer from going to sleep without changing system settings. It has features such as one-click activation/deactivation, a schedule deactivation, a menu icon with commands, and no processor time waste. It is Gatekeeper enabled and warns that using the Mac with the lid closed can lead to serious system heat problems.