After reading so many differing opinions on this subject, I asked the manufacturer, in my case Hegel, if there was any harm caused by leaving my H30 Mono amps powered on 24/7, and is the rush of current at startup more harmful than constant power. Their answer was this. The amps are not damaged by the on/off cycle. They recommend waiting 60 seconds between turning on, if you have turned off. They did advise against leaving powered on 24/7 citing a waste of electricity and shortened life span due to constant heat. Therefore in my own case, I turn off after listening and turn on a couple hours in advance of my next session.
Maybe someone could answer this question for me. Define "shortened" lifespan. My previous Parasound power amp lasted 20 years without any issues and then I sold it. If shortened lifespan means lasting 25 years instead of 30, then I’m now too old to care as either one will out live me.