Don’t have much to add here, as about everything has been said!
For me, I turn off all of my tube gear (4 power amps and 3 preamps) when I don’t plan to listen to it within the next 2 hours. To my ears, all of my tube gear sounds great within 10-15 minutes of powering on. Some say an hour, I just don’t hear any difference of 15 minutes of warm up vs 60 minutes. The temps inside the tubes are pretty warm within 15 minutes.
I do know a guy who runs his preamps 24x7 and has for about 10 years now. Over 150,000 hours on his tubes and they still test as very good. I also know people with tube preamps from the 60s which still have their original tube sets in them - not run night & day for 50 years, but used a lot along the way - and powered on and off thousands of times. Some tubes do have very long lives!
Personally, I've never had a preamp tube burn out so I don't know how long they last.
For me, I turn off all of my tube gear (4 power amps and 3 preamps) when I don’t plan to listen to it within the next 2 hours. To my ears, all of my tube gear sounds great within 10-15 minutes of powering on. Some say an hour, I just don’t hear any difference of 15 minutes of warm up vs 60 minutes. The temps inside the tubes are pretty warm within 15 minutes.
I do know a guy who runs his preamps 24x7 and has for about 10 years now. Over 150,000 hours on his tubes and they still test as very good. I also know people with tube preamps from the 60s which still have their original tube sets in them - not run night & day for 50 years, but used a lot along the way - and powered on and off thousands of times. Some tubes do have very long lives!
Personally, I've never had a preamp tube burn out so I don't know how long they last.