Stanwal - I stated what capacitor companies claim. Going bad when not used, that you mentioned, has place when you not use amp for long time (years) and aluminum oxide layer (serving as isolator) depletes eventually lowering allowable voltage and causing short at operating voltage - often exploding from the heat build-up. Caps have fuse (rubber plug) to prevent explosion. It is recommended in such cases to start at lower voltage (Variable transformer) until aluminum oxide layer will build-up again. Unfortunately some power supplies like SMPS either start or not and varying line voltage might not help much.
It is very difficult to compare performance of 25 year old amp with exactly same new one. I replaced power supply cap in old SS amp and got bass control and dynamics I didn't know it had.
I think that capacitors are just drying up and the temperature accelerates it. It might not fail ever but performance will slowly deteriorate since caps ESR rises up (thats why people recap their amps).
It is very difficult to compare performance of 25 year old amp with exactly same new one. I replaced power supply cap in old SS amp and got bass control and dynamics I didn't know it had.
I think that capacitors are just drying up and the temperature accelerates it. It might not fail ever but performance will slowly deteriorate since caps ESR rises up (thats why people recap their amps).