Threshold amp tune up?

Just wondering what the life expectancy of a higher quality amp is before requiring a rebuild or "tune up" so to speak and what signs are there to listen for that may tell you that things are starting to get a little old? I have a Threshold S350e that is about 12 years old. I can't say that I notice any degradation of sound quality from new but unless there is a drastic change you likely would not notice much af a change when you regularly listen to the same amp. It does generate a fair amount of heat and I often wonder what effects this may have on the sound over the long run. I guess "if it aint broke don't fix it" but I'm just curious and would like to hear a few opinions on this subject.
It will ne re-capping and that vintage usually needs a new power switch. There are other things that can be done, but those two things should keep it going just fine for another 10-12 years.