I did a lot of auditioning of both low level tubes and power tubes in preamp, power amp and phono stage, and found that there was no reliable general rule - some brands sounded better in one use and another in a different use. It is cheap to try some of the tubes so I bought two or three different ones just to see what was what and used the ones I preferred (based on blind listening by myself and another person).
Auditioning power output tubes could get pretty expensive, though....
Tube life in most gear is quite good - and in some applications they seem to last forever without deterioration. In phono stages, for instance, you'd have to be a vinyl nut that played for hours every day to age out the tubes in a decade.
As was stated, though, it does depend on the amp design and how highly 'stressed' a tube may be in a given application - push the voltage and shorten the life.
Auditioning power output tubes could get pretty expensive, though....
Tube life in most gear is quite good - and in some applications they seem to last forever without deterioration. In phono stages, for instance, you'd have to be a vinyl nut that played for hours every day to age out the tubes in a decade.
As was stated, though, it does depend on the amp design and how highly 'stressed' a tube may be in a given application - push the voltage and shorten the life.