Thanks to all who responded -- it was very educational. The preamp I'm considering does in fact have a standby mode, so I'm going to leave it powered up as several of you suggested.
mixing tubes and transistors
I'm considering getting a tube preamp in an otherwise all solid state system. The solid state gear is designed to be left on all the time. The tubes in the preamp wouldn't last very long if left powered up all the time. Here's my dilemma: the power amp owner's manual says to power down the components in sequence from the speakers "backward" to the source. The preamp is in the middle of this chain. If I turn off the preamp (to extend tube life) while leaving the amp and sources on (to keep the transistors thermo-electrically stable) am I creating any electrical hazards for my equipment? Please advise, and thanks.