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

There are 2 parts of the equation. The amount of power dissipated by the plate is determined by the class of operation as stated above. Class A amps like SETs consume maximum at idle and push pull amps minimum at idle.

However, in all case the filament and cathode is sitting there cooking away so even a push pull amp tube will eventually burn out even if you never pass a signal through it.

yioryos, your exclamation point made me wonder if you find some lack of credibility to beavis' assertion that he listens at @85db. i do not know why beavis mentioned this but many of us do own meters for kicks and also to conduct objective tests on overpowering amps as well as a myriad of other useful comparative tests. personally i think anyone involved in 'hi end' stereo sound would find it VERY informative to have a SPL meter laying around. they can answer a lot of sonic questions accurately and save a lot of time. just my 2 cents. i keep it next to my remote(s) and refer to it for kicks eg. if i decide to measure a loud passage to find out how loud it 'really' was.

A meter is critical for getting correct placement in your room for the smoothest spectral balance - especially important for get the bass right - but this is off thread. I think that tubes in Class A is not affected by loudness, other than clipping, and A/B is. Probably a good question to ask at Audio Asylum in the "Tubes" scetion.

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.