It’s the caps that fail. Electrolytic caps have the highest failure rate of any passive component. My team tries to avoid them in our designs as much as possible. But you’re right, caps in a good design can easily last 20 years, making a power supply the longest lasting component of most builds.

My go to source for reviews was always jonnyguru.com but he closed up shop. Not sure who’s actually doing in-depth performance and component reviews these days.