Like most blanket statements, its no true but has some kernel of truth. Class-A amps typically run hot because they dissipate 100% (actually in most cases, 200%) of their rated power all the time. But that is a design condition and ought to be accounted for so that it is irrelevant.
Depending on how they are designed, cooled and parts chosen, class-A operation, and its attendant heat generation, can have very little effect - or can be a long term issue. I have hundreds of units that I designed in the field, many approaching 30 or over 30 years old with essentially no failures due to accumulated heat. While these are not pure class-A, they are very high bias amplifiers that dissipate a LOT of power; but they are designed for it.
The primary components harmed by heat are electrolytic capacitors. transistors can run very hot with no ill effect, and most resistors can too unless the are directly over-powered (e.g. run at or near their rating or 1/4w, 1/2w or whatever). Film caps too typically are immune unless its so hot they melt -- and that's HOT.
I'm sure there are some poorly designed amps out there. Avoid them :-)
Depending on how they are designed, cooled and parts chosen, class-A operation, and its attendant heat generation, can have very little effect - or can be a long term issue. I have hundreds of units that I designed in the field, many approaching 30 or over 30 years old with essentially no failures due to accumulated heat. While these are not pure class-A, they are very high bias amplifiers that dissipate a LOT of power; but they are designed for it.
The primary components harmed by heat are electrolytic capacitors. transistors can run very hot with no ill effect, and most resistors can too unless the are directly over-powered (e.g. run at or near their rating or 1/4w, 1/2w or whatever). Film caps too typically are immune unless its so hot they melt -- and that's HOT.
I'm sure there are some poorly designed amps out there. Avoid them :-)