I substantially agree with Jfrech. Mine is a tradeoff. I use a very difficult to obtain tube with a 10,000 hours usable life. This is about a year and a half when always on. It takes my preamp about 2 hours to reach its peak, and I typically use it for 3 hours each night and about 5 hours each weekend. Thus I use about 41 hours per week turning it on and off, rather than 168 hours leaving it on. My tubes thus will last about 5 years.
