#1
My ValveKing has tube covers (preamp tubes only) like the ones on this head:



Are these good or bad for the tubes? I would assume that they trap heat and would therefore reduce the lifespan of the tubes.
Epiphone G-400
GFS Crunchy PAF - Bridge

DigiTech Bad Monkey
iSP Decimator

New Amp Fund: Depleted
#3
Those covers let in less noise. Some tubes are microphonic and will caputure som of the sound surrounding the tubes. I have one on my VM.

I dunno if all the tubes in that head are microphonic though. Some tubes are and some aren't. We'll.... they are all, but more so than others.
Guitars:
Epiphone Elitist Les Paul Custom WCR and Dimarzio equipped
Amp:
Marshall 2266 Vintage Modern
Marshall 1960TV
Effects:
Dunlop Crybaby From Hell