Should an audio system be left on at all times?

Interesting. I listen to music pretty much every evening I am home. That would mean turning the system on and off everyday. I agree with other posts that it takes time for the wires to warm up (I have long runs of speaker cable), so what is the difference in waiting for the amp and other electronics to come to operating temperature too? I have been leaving my gear on thinking it was better for longevity. Maybe its time to rethink that.

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).

Stanwall - Check this link: http://www.dfrsolutions.com/pdfs/Uprating_of_Electrolytic_Capacitors.pdf

They mention temperature as main factor (and 10 deg C rule). ESR while getting lower at high temperatures (might explain reason for warmup) eventually gets higher from electrolyte evaporation.

Good quality amp equipped with 105 deg C caps might last for very long time while luke warm. I would like to preserve my amp at current state as long as I can.

Well, no matter what, having your amp off most of the time will save electricity. You can use the money you save on your power bill to go stimulate the economy...

Maybe if it's solid state, I wouldn't if it is tubed equipment, why waste the life of the tubes? I never understood what the advantage was to leaving it on. I have tubed equipment that I turn on about an hour before I want to listen to music, that seems to be enough warm up time. Even it I wanted to keep it on, my wife would never feel comfortable leaving the house all day with equipment turned on, afraid of a fire or something to that effect.