The life specification for an electrolytic capacitor is based on operation at the maximum ambient operating temperature of 85C or 105C. For every 10C reduction in ambient temp, the life doubles, so when you get down to normal temps in a class AB amp you get 20+ years easy. No problem to leave them on.
Where I work we have many 30 year old machines that are always on - 24/7/365 and their original linear power supplies with big electrolytic caps are still working fine.
Check this:
https://www.xppower.com/resources/blog/electrolytic-capacitor-lifetime-in-power-supplies#:~:text=Manufacturers of electrolytic capacitors specify,to 10,000 hours or more.
Case in point, I had a customer who brought in a Bryston 3B amplifier with the complaint "no bass". He'd told me that the amplifier had been powered on continuously since he bought it in 1982. When I put the amplifier on the analyzer, sure enough, the amplifier started to roll off at 6dB/oct starting below 20KHz.
During troubleshooting, I observed that most of the components inside the amplifier looked like they'd been fired in a kiln. Every one of the 16 220uF capacitors read in the picofarad range when I tested them on a capacitance bridge after removal. I replaced all the caps, some burned resistors and retested the amp. It now was ruler flat across the entire audio range.
So, my opinion is that you amplifier will last longest with moderate usage, a couple hours a day and off when not in use.
Very interesting. I’ve often thought it would be a worthwhile effort to have a comparator based protection circuit that referenced the output versus input, to protect against abnormal operation. A mosfet switch at the speaker output would be a good way to finish it off.