A question I suspect reveals a lot of ignorance...

If your amplifier is class A, the volume setting will have little effect on tube life.

With any other class of operation, the higher the volume setting, the shorter the life of the tubes, although other factors such as the actual bias level of the tubes, how optimally they are loaded to the speaker and how well ventilated they are can play a bigger role. It all makes a difference.

Generally speaking, the warmup you hear in a tube amp has more to do with the tubes and the filter caps in the amp than anything else. Most tube amps are doing fairly well after 45 minutes and most have gotten to where they are going by about 3 hours.

Thanks to all.
Viridian, Herman & Atmasphere - seems like you all agree tube life in Class AB amp service is affected by volume level. Guess I'll look into buying some spare tubes!!

Dpac 996 - Don't know what ill effects cranking things up prior to full warm up might have. BUT I too hear an improvement after things have been running a while. Seems a common experience with tubes - but I also thought that with a solid state receiver I ran in the past - the sound opens up. After 1 hr for sure...but I think after a few hours, there is another step change. No quantitative data to back this up - just an overall impression.

Good listening to all.

Don't tubes draw the same amount of current at all times when they are biased correctly? Otherwise biasing would only matter when the amp is not playing.

Don't know the answer either, but would like to ask whether anyone knows whether or not it is ok to immediately play the amp after switching it on? I seem to recall reading somewhere that a tube amp should be allowed to warm up a few minutes before receiving a signal...

Don't tubes draw the same amount of current at all times when they are biased correctly?

No

whether or not it is ok to immediately play the amp after switching it on

It won't hurt it. It just won't sound right.