Tube life

Running several tube amps for close to 30 years now I have sometimes replaced tubes early (few hundred hours) more often replaced them after a few years (thousand hours plus) sometimes even run till they died. Almost always it seemed if they degraded at all it was way too slight and slow to notice. Trying new tubes hoping to improve the sound almost always is a total waste of time. Its not that there aren’t differences. Its that the differences are too slight to bother with. And I will bother with an awful lot of really minor stuff. But the difference between tubes, its a crapshoot but in general there is less difference between tubes than between the same tube new out of the box and after running a few hours. The best tube of all I have tried is the JJ, which is also the cheapest. Tube rolling, hoping for some sort of transformatory revelation, is just nuts.

Unless you spent $1300 for your 300-B. Those of course are totally worth it. Eyeroll.

Small signal tube life, (example 12AX7 and 12AT7), for new production tubes is about 4000 hours average. NOS signal tubes from the 1950s, 1960s are said to average up to 10,000 hours of life.

The average tube life depends on how hard the designer of the amp pushes the tube in the circuit design.

New signal tubes as a rule gradually wear out slowly over time.

" Trying new tubes hoping to improve the sound almost always is a total waste of time. Its not that there aren’t differences. Its that the differences are too slight to bother with. "
Guess I've had difference experiences than you with swapping tubes, for me there have been noticeable differences whether signal or power tubes.

@jrod68Here's
@jrod68H@jrod68Ha@jrod68H@jrod68H link to Brent Jessee's website (I'm only a customer) but he provides listening impressions to various brands within the specific tube type - might be helpful to you

Thanks for the comments (so far).  I can't tell you how much I'm enjoying my McIntosh MA252 with the Maggie 1.7s.