My understanding, from reading posts by those far more knowledgeable than me, is that turning tube amps on and off for short periods is not advisable (I don’t mean to suggest you’d do this, I’m just putting the warning out there in case it helps others).
Here’s the advice of an expert:
Tube heaters are stressed every power on cycle. Tube heaters wear out over time when they are powered on. My rule of thumb is to leave on if I intend to keep using throughout the day, though intermittently. When it is likely that I won’t use the amp for at least eight hours, I turn it off.
And here’s the source.