I'm not an electronics expert but I thought that heat cycles (on, off, on, off, on off) were a major electronics killer.... so leaving an amp on 100% of the time is good for longevity; right?

Most of the new audio electronics IMO including Onkyo, Denon, etc is trash. I have 3 new Crowns made in communist china (500wpc x 2 @ 8ohms) and they are solid performers. My Lansing re-coner in NJ who sells Crown tells me they are garbage, and that nobody wants Chinese Crown amps, however.