Recapping your amp

Sounds like you are indeed close to that timing belt failure moment.

Yea but when to replace it before or after it goes.

A timing belt won’t degrade your engine’s performance, before it fails(completely). The point of my references was, that(electrolytic) capacitors do. Of course: to many, "...still working...", is good enough. Do you replace your racing tires, AFTER they blow out, or- as soon as they begin to lose traction?  One's course of action, will depend on how much they value performance(different strokes...).

As with timing belt, replace before it goes. A failed power supply capacitor can blow up a speaker, and a leaking one can mess up the amplifier’s board. Before that, you will have lost some dynamics, of course.

Teo - Regarding my speaker recap, the capacitors and resistors were approved by the original desiger.  Sonic caps and mills reisistors superior to originals used in the 80's and 90's but it did change the character of the sound for the worse for me anyway.