In general for tube amps it's better to turn them off. With one exception that I know. David Berning's amps. David designs for long life, very, very long life in total contrast to almost every other tube designer. I know from a friend who was there that David's first amp , the Audionics BA150, would last almost forever. The prototype was turned on in 1972 and turned off in 1977 and there was no measurable wear on the output tubes.
Leaving my amplifier on ok?
Would it be ok to leave my amplifier on all the time if I want to extend the reliability of the amp? Many amplifiers ar Class A, high current bias and tubes might be a problem if energy consumption is a factor. Not to mention Excessive heat from bias operation. Is it possible to extend the life of the amp with leaving it on all the time?