Questions from a Tube Preamp newbie

As an aside, I like all the JJs I’ve had (all preamp or driver small tubes) except the KT77s, as they lasted about one day in my Dennis Had se amp before I rejected them. They are cheap however...after I recovered from that experience with 77s I eventually bought a pair of the Gold Lions and they’re the best of any type (88s, 120s, 150s, etc.) of anything I’ve tried in that amp...a very nice tube indeed.

I never leave tube amps on when I'm not around as I've had small signal (preamp) tube commit "tubicide"…once in a guitar amp I left on after a rehearsal (for a week) and that amp never really recovered (sad), and another time a well regarded new-ish NOS Phillips AT7 killed itself right on front of me during a listening session…jumped up and shut down the amp before any damage happened. If tubes have a break-in period I'm not aware of that as they seem to display whatever their tonal characteristics are pretty much right off the bat, although the rest of the amp might need warm up. I noticed this when swapping out tubes having just shut an amp down to let it cool a bit…many many hours can be gleaned from a hard driven signal tube, proven by guitar players everywhere when you'd just forget about 'em until the amp starts to get weird…years...