Lifespan of a quality solid state amplifier?

Bifwynne, No input signal is OK. Tube amps need load, SS amps don't.

SS amp might fail when input signal is present and output shorted (overcurrent). I've heard that some poorly designed class D amps might go into oscillation without load but likely will survive that.

Tube amp might fail when input is present and output is open (overvoltage). It might even happen without input signal if amp goes into oscillation.

I increase volume slowly, at first, making sure I hear the sound from both channels. It is good habit, IMHO, since things tend to get shorted or disconnected between listening sessions.

My personal experience of owning SS gear for many years is that leaving gear on 24/7 is silly, wasteful, completely unnecessary, tawdry, untoward, and pretty much unjustified by any meaningful data ...the wasted juice far exceeds the cost of any "premature ageing" of a component due to turning it on and off.

I had an AR receiver that worked for 35 years and was still working when I sold it. (Acoustic Research.)

Filter capacitors have a half life of about 20 years. What that means is that in a 20 year period, about half of the caps will have failed. This is true of transistor and tube amps.

Sometimes when the cap fails the ESR goes up like Kijanki was talking about, you can also have the experience of the cap slowly loosing its capacitance. This may not result in the hum that is commonly associated with filter cap failure, but it will impose sonic degradation as the power supply is no longer properly bypassed. This can increase distortion and affect bandwidth, things that you may not notice over time but would certainly show up on the bench.

So in general, by the time a piece is 15 years old, there will be some degradation or outright failure, by the time 20 years has passed the chances of that are 50/50. This will be true even if the unit has been in continuous use, although such pieces in general do have the caps last longer, that's not the same as saying they actually still meet spec!

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Ralph, can you back that up with some references?

Curious where you got 1/2 fail in 20 years.

Even if true, given that the lifetime of a particular cap is inversely proportional to operating voltage and temperature I fail to see how this is useful for predicting the lifetime in any particular piece of equipment.

BTW that is not the definition of half life.

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