Leaving tube amps on.

@tattooedtrackman  , on bias and red plating,

a few years ago (I think it may have been some time in '20, I had a coupling cap fail on one side of my Cary V12..  I won't try to explain the science or theory of whatever happened within the circuit, because that kind of stuff is beyond me, but the result that I saw was the bias on that side running away high regardless of the position of the bias pot.  (I could back the bias pot all the way off, but shortly after turning the amp 'on' the bias would start climbing out of control on that side.  The tubes on that side got very hot--red plated--and were never the same sounding after I replaced the cap.  I felt the tubes were getting tired anyway, but that event was the last straw and I bought new tubes.  

@tattooedtrackman A number of years ago I bought a preowned tube amp that according to the manual to set the bias you had to put a tiny phillips head screwdriver in a tiny hole until you blindly felt the phillips head screwdriver engage into the phillips head bias screw.  Then turn the screw until the amp shows proper bias for that channel.  Unknown to myself the previous owner had had a bias pot replaced with one with a normal slotted screw.

Well first time biasing I broke off some part of the bias pot and a second later.  I was met with smoke, smell and a real fireworks show. I hit the on/off button and that did nothing to stop what was happening.  I then pulled the plug and the show was over.

If you really saw and smelled what occurs when something like this happens you would not even want to think of leaving your tube amps on and unattended for a long period of time.

Surprisingly the cost to repair the amp was minimal.

What I generally do with tubed gear, which I've done for eons, is turn the gear on around dinner-time (if I plan to listen to music) and off after listening.  On the weekends I'll turn them on earlier and leave on all day and off before bed.

@jetter   Read my post from last year about when I first bought my Ref 750s. I had a tube arc from a bad KT150. 

@tattooedtrackman  My bad, I did read about it back then but forgot about your personal fourth of July.

If I was not there at the time it could have easily resulted in a serious fire.