Tube pre-amps: turn off when not in use?

I turn all my tube gear off when not in use. Tube gear gets warmed up pretty quickly, as compared to solid state, so there is less of a reason to leave the stuff on all the time.

All of my tube gear uses tube rectification, so the turn on is relatively gentle, and the life of the tubes is not being shortened by the turnon/turnoff cycle as much as would be the case with solid state rectification. I have not looked into use of thermistors to make the ramp up even more gentle, but if I did, there would be no doubt that turning the stuff off would greatly extend the life of the tubes.

Tubes do wear out when left on. The output tubes on an amp may last something on the order of 1,500 to 2,000 hours or so. The smaller tubes used in preamps will last much longer. 5,000 to 10,000 hours and more is probably not unreasonable. (There are just shy of 9,000 hours in a year.) Some specialty tubes can last tens of thousands of hours, but your equipment probably doesn't have tubes of that nature.

So, the question is how often you want to replace tubes and also how much electricity you wish to use. Your personal listening style is also a factor. If you reliably don't listen after you go to bed and until you come home from work the next day, why waste tube life on the three-quarters of the day when you are sure you won't be listening? However, if you are always home and often listen at the spur of the moment at any hour of the day or night, it may well be worth it to you to leave the system on continuously.

I own 2 tubed pre-amps, which, in the past, I have left on continuosly. The tube life on both of these units used in this fashion is about 1 year. Now that I am using NOS tubes, I turn the pre-amps off when not in use.

I turn mine off when not in use. Have you seen the price of NOS 6H30's? At $200/pop, it'll cost you $800 to re-tube your VK-31SE with them.

for tube pre-amp-- its ok to turn off when not in use.
for solid state pre-amp-- its better to leave on all the time. These takes time to warm up.