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.
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.