If it works doesn't mean it's not broken, as has been demonstrated with recent Cyrus kit.
The achilles heel of amplifiers like all electronics are the electrolytic caps. Good quality Japanese caps should soldier through 10+ years in a Class AB amp with no problem. More heat means less longevity. After 10 years of regular daily use, one should consider general checkup of state of electrolytic caps, cracked solder joints, heat spots and other possible ills.
Maintanance every 5 years should be simple cleaning dust, cleaning open type switches, relays and potentiometers (closed type not as frequent). Bias and DC offset should be checked and reset if its off. Such process doesn't take more than 1 hour.
Speaker cable and interconnects should be plugged/unplugged once a year to clean oxidation. Cleaning with isopropyl alcohol or specialty sprays is also a good idea. If the speaker cables are bare wire, it's good idea to cut and strip fresh ends say every 2 years. Shouldn't take you more than 5-10 mins.
Western culture has moved to disposable goods. Cars are bought, abused for 10 years and ditched, typically with no maintanance inbetween. Electronics flood garbage disposal sites. The profession of electronics repair tech has essentially dissapeared. In economies of scale everything is made to survive the warranty period and no more.
Due to this new way of thinking about material goods, I see how my suggestion about maintanance might sound waste of time and pedantic OCD rituals of no benefit. But since the OP asked I thought I'd share my practice.