@soix "..but I know some other manufacturers recommend turning it off so may be product specific (obviously you don’t wanna leave a Class A or tube amp on). Anyway, I’m with you on just leaving it on."
My primary all-tube system with tube preamplifier and mono tube amps have easily accessible on/off power switches. Warms for 45m prior to use, does ok.
Now the secondary system I’m working on now, solid state Class A amp has a power switch on front, and yet the matching Class A preamp has no power switch at all. Plug in the preamp, and it’s left powered on all of the time, as designed.
I can honestly say both systems do sound better, or at their best, when all of the components are good and warm, big iron transformers extra warm and saturated at 4+ hours. What was odd and memorable was rechecking after being left on for 24hrs, could usually hear something a little extra special or more engaging each time. Same occurred with many of my former Class A/AB dual mono solid state amps. Reaching that optimum sustained operating temperature perhaps. I try not to leave any of them on though for more than 4 days max, if I know I’m not gonna use it for a week or more fwtw.