One of the things that annoys me is when my laptop sleeps while I’m working. On OSX I used Caffeine to stop that from happening and had it autostart every time I booted the computer up.

With ElementaryOS (and Ubuntu) the application your looking for is called Caffeine Indicator. I still haven’t been able to automatically activate it on boot. Sure it starts by flagging it as a startup application, but it doesn’t automatically stop sleep.

You may wonder why I don’t do this by turning all the power settings to never let the computer sleep. 99% of the time I don’t want my laptop to sleep but once in a while I do want it to sleep. It’s much easier to simply turn off Caffeine Indicator and then let it sleep as it wills than to fiddle with the power settings.

You can find Caffeine Indicator in the AppCenter in ElementaryOS.