Should an audio system be left on at all times?

My system consists of a solid state cdp, solid state amps, and a tube preamp. I usually end up listening to music almost every night when I get home. Is the general consensus that I should keep everything except the tube preamp on at all times due to the high frequency of usage? My tube preamp is actually from Odyssey and the guy from Odyssey said that his co-worker's tube in the same preamp has lasted a year and a half so far and that it has yet to be turned off.

Actually, I asked about both longevity and performance. While some of us may be able to replace a system when it breaks down, I probably will not be able to replace my system with anything comparable for a long time to come.