By "a matter of degree" I meant (along with a lame pun) the degree to which you're using the amp...running into a 4 ohm load to get 115db peaks for 5 hours might cause more heat than a day of light background music. I have a later MOSFET Forte' A/B that get toasty-ish only when I play something kinda loud for a while, but unless you have the amp in a VERY hot room I'd think excessive heat (risking shut down) is a design flaw, and the amp designer should have included fans. I'm amazed that some "all Class A" amps don't melt in "normal" use...but maybe I'm easily amazed.
