Heat in class A equipment

44 years for Phase Linear.

Life of electrolytic caps shortens by 2 for each 10degC increase, starting likely from 50 years. Other than cap replacement from time to time, you should not worry - electronics should last.  I have espresso machine constantly on for the last 10 years. It is very hot to touch and has electronics inside (microcontroller). It is still working and I expect at least another 10 years from it

It's thermal cycling that kill electronics faster than staying at a constant temperature. Think you did a post awhile back about capacitor life?

IR imaging and other direct temperature measuring techniques are used to detect hot spots in equipment and power distribution systems. Opening the equipment to see whatever it is you are looking for is wasting your time unless you know what you are doing and looking for. Enjoy the music instead.