SS takes days to sound its best. Days. With tubes it is more like hours. With records there is the motor. When you hear improvement across the first side of a record, that's why. Try turning it on, spinning the platter an hour or so. There will still be some improvement, but not nearly as much, and starting from a much higher level. The difference is the motor - and controller circuits - being warmed up.
rule of thumb: how long do you leave a tube preamp on versus turning it off then back on?
I just upgraded to an Audio Research REF 10 with 12 tubes and I am wondering how to best preserve the tubes. How long sitting turned on is equal to the wear and tear of turning it off then on again? I had a Rogue RP 7 with just four tubes so I didn't worry about this issue so much, I just turned it on when I began to listen then off at the end of the evening. Now I'm wondering where the sweet spot is? Away for a hour, two, three, turn it off when? Am I over-thinking this issue?