Tube pre-amps: turn off when not in use?

It could depend on the component and/or the manufacturer's recommendation.

When I owned a Kora Hermes DAC with two 6922 tubes I left it on coninuously for the four years I owned it without problem, even when fitted with NOS CCas, etc. But the tube preamps I've owned I always kept off when not in use.

The preamp I currently own uses two 6SN7 tubes and generates a decent amount of heat so I always turn it off. Plus the WWII era VT231s in that preamp won't last more than 6 months if left on all the time.

Bsmith15, when I was hot and heavy into listening to my system, especially during colder parts of the year relative to LA, I'd do exactly what you do.

Adamg, in my experience with 6922s in a DAC I was able to leave them on continuously for four straight years without excessive wear. When I owned a BAT VK3i its 6922s didn't seem to wear prematurely from being left on all the time. The complete opposite was true of my 6SN7 preamp which burned through expensive tubes if I left it on for too long. I am not familiar with the characteristics of the 6H30 which I believe your preamp uses.