Power/Preamp..switch off or on when I'm out ?

I think amps sounds better when they are left on . However is it generally better to switch them off ( even on standby ) when I don't use them for a few days or leave them on completely ?
I am using an NAD C 160 and NAD C272 .
But for my question that really doesn't matter .
I never turn SS equipment off, tubes ofcourse are diffrent, unless I am away for days, everything stays on.
Optional, but not Class-A amps (power consumption and heat/component lifespan) or tube equipment (tube lifespan).