Lifespan of a quality solid state amplifier?

Even inexpensive solid state amps and preamps seem to last essentially forever.

Hopefully one of the A'gon techies will chime in, but FWIW, here's my thought. SS does age. I base this view on the "care and feeding" I occasionally do with my old Crown DC300A. For those old-heads out there, you know this amp - it's immortal and bomb proof. Nevertheless, the last time I sent it to the Crown factory for a "grease and lube," they replaced some of the old electrlytics, believe or not, the power supply caps and a couple of transistors. The stats are incredible, thank G-d for NF.

I am still (as a backup) using some 25+ year old SS amps and they still work fine other a higher noise floor due to aging caps in the pre/amp sections. While I don't think this is unusual, I would say the most amps of either SS/tube nature are pretty reliable. Other than tubes themselves, the main components that age are the capacitors. Strangely two factors can effect their longevity, one is heat-which would logically take a bigger toll in tube amps or class A biased higher power amps. The other killer is lack of use as the caps will dry out. Many people advocate using a Variac to bring power back to an amp that has been idle for an extended time to bring the caps back up to life slowly as a sudden rush of current could blow them. I've also noted that amps with several smaller output caps (as opposed to fewer but larger caps) are less susceptible to aging -don't know why...

Spinaker01 - Drying of the electrolyte increases ESR of capacitor. When it gets into many ohm range it becomes very audible and after that it might even go to thermal runaway since current going thru cap x ESR = Heat but temperature increases ESR (positive feedback). Smaller caps are connected in parallel making ESR lower to start with - less audible when old.

Each 10degC of temperature increase cuts life of capacitor in half.

Electrolyte inside of a cap eats out aluminum oxide (dielectric) lowering breakdown voltage. Presence of voltage rebuilds this layer.

I always change the electrolytics when I buy used. When they get tired, the music gets tired.