Best temperature for optimum tube performance

Ever look at a "combo" guitar amp? For example, a Fender Twin Reverb (I’ve owned and abused a couple of these) has 4 6L6 power tubes and 6 preamp tubes, all mounted upside down venting heat into the amp (although they’re uncovered...still...), and if you tilt it back it’s worse heat wise...but my amps never failed to work tirelessly. Kinda makes hifi stuff look weirdly delicate and wimpy...vibration? The amp is also in the same space as 2 12" speakers and still manages to work...all night...

Something not going right for you?

Lol!

My three ARC amps (NOT TUBES) each have 32 output transistors and 3 cooling fans each.  So, 96 output transistors and nine cooling fans.  If I run them really hard for say an hour their temp never goes over 100 F.  Yes, I measure them with a BBQ probe remotely.

Although this does not speak to tubes directly, I would say that if the interior of your cabinet is close to the ambient temperature of the room
you are good to go.

A remote thermometer is very cheap and worth it if you are asking the question.  Start out cold and log the temps against time as well as noting room temp.

Let the snarking begin!

Regards,
barts

Put your gear in a ventilated wood rack and watch how much better your tube gear sounds.

Room temperature?? Never concerned myself with this really.