Sometimes I would fall asleep when using my tube amp and it would stay on all night. So I gave one of these a try. It works good.

http://www.amazon.com/Belkin-Conserve-Socket-F7C009q-Energy-Saving/dp/B003P2UMS0

I've done the same thing. Tube amps at night rock! That's a good idea because having the vacuum tubes operating for that extended period for no reason is not good for their longevity.