I have a pair of JC 1s which are now driving my subwoofers. I used them on my ESLs for many years and I can tell you that there are very few amps that perform as well and the ones that do cost way more. They may go down as the amplifier value of the century. No JC 1 is old enough to need new capacitors at this time unless the amp was damaged. As long as the amps are running as advertised and there is no evidence of physical damage you should be good to go. They are built extremely well and use extremely high quality output devices. The thermal cut off is set pretty low so there is no way they can be damaged by heat. They would just shut themselves off and flash a red light at you. I see no reason why a JC 1 should not run reliably for 30-40 years maybe more.
Sound wise these amps have an airy effortless like a high powered tube amp but the fist of a high powered solid state amp. God knows how John Curl does this. I'd love to hear some of his Constellation designs. Of all the amps I have been able to hear in my system only Pass amps have that airy effortlessness that I find intoxicating. The JC 1 has phenomenal
(better) bass which is why they wound up on the subs and boy do they do a honking job of it. Unless you are use to hearing high powered Pass, CH, Boulder, Soulution, or Moon amps these things will absolutely blow you away.
Mike