Start with MTBF (mean time between failure) I have a 44 year old laser printer, shut down twice for clean/lube/PM.
It stays on 24-7. 4X longer than average lifespan. My 30 year old oscilloscope, Runs 24-7, brightness off to keep the CRT from burnin. Still meets specs. 30 year old spectrum analyzer, same as the scope.
A Compaq laptop, 7 years, never shut down, recycled after keyboard fail.
All of this stuff twice the life expectancy or better, a few very minor problems.
Analog power supplies practically never fail operated within their limits.
Other equipment that rarely gets used stays off save for their use.
The reasoning: power surges, thermal changes are the hardest on electronics. poor solder connections can open, micro cracks in traces can open, all causing some failure. An auto engineer once said the wort thing you can do to an auto engine is to start it, the second worst, shutting it down.