Should I replace capacitors in an old but working amp?

I have an Ensemble Tiger B50 amp which I purchased new back in the early 90s.   I love the way it sounds and really just want to keep it for as long as possible.   I leave it on at all times.
My question is should I just keep on keeping on or should I be replacing the capacitors after all these years.   I hate to mess with it as it sounds really good to me but I don't want it to burn up  either.

Thanks,
Steve