When it's time to change the power supply caps, your amp will let you know with a loss of bass definition soon followed by buzzing/humming. Until then, leave it alone if it works and there is no sign of physical damage.
re capping
I hear the phrase 'recapping'. when do you know when you should 're cap' an amplifier? I have a McIntosh mc602 amp that sounds fine to me. I also have a McIntosh mx132 that works ok for me. I also have a bose 901 series 2 active equalizer that seems to work ok. the 'red' on light kinda flashes now and then. if my system sounds ok, should I worry about my units?