Turn them off. Heat and cost matter.
The exception to this is some Class D, like ICEpower which absolutely sound bad until they have warmed up for 2-4 days. Can't explain this in any logical way. 
Leave it on?
I just listened to Paul McGowan explain that turning SS equipment on and off degrades the capacitors from the tiny power surge and that leaving SS equipment on ALL THE TIME is best. What do you do?