When they get to 15 years on you could start having problems. Take for example the caps that are in close proximity to voltage regulators they can get hot in temperature and dry out.

So there are a few things you could experience. One as you stated where you could get a fault on a amplifier board but also a drop off in sound quality.

I have a pair of old 5ks stamped with the Clifton road address and compared to a newer pair of 5ks they sound terrible. So they will be treated to a cap upgrade soon.

This is one of the things I offer. Cap upgrades on amps and DSP's.

Cheers chris

561m, D5k fronts, Pair 205's running 2 x Scandyna micropod se centers. The Ball! Scandyna Sub. Matching Scandyna rears with Boss car power amp.
Ex. Meridian service engineer.