My Pass XA 60.8 power amps take an hour to warm up and the sound quality improves slghtly over the next hour. There are no further gains to be made from leaving the amplifiers on when not being used from listening - except for warming up the room, but that's a very expensive form of space heating and not recommended.
Amp — Leave on or turn off
I always turned my Benchmark AHB2 amp off after use every night. After all, why is there an on off switch on the front panel if not to do that? Last night I accidentally left it on. This morning, when I played my first record, I couldn’t believe my ears. The same record I played last night sounded infinitely better. I tried a second record and that, too, was much better.
I know there’s a debate on the question of leaving an amp on all the time.
I now know where I stand!