Wimoweh is a menu-bar application that allows you to have better control over how your Mac sleeps.
Shows which apps are preventing your Mac from sleeping and why.
Stay awake based on average CPU usage over time.
Stay awake based on available services on your local network
Set-up a countdown to keep your Mac awake for a certain amount of time
Allows you to always stay awake when certain applications are running and automatically sleep when they’ve finished. This is great for apps that OS X seems to ‘ignore’ even though they’re working or if you’re waiting for a lengthy job to finish and want the Mac to sleep afterwards.
And of course, you can just keep your Mac awake indefinitely.