Leaving the amps on generally makes 'em sound better, but some do stabilize after an hour or so to the point where leaving them on longer makes no difference. Depends what you have; my Levinson mono's sound their best after 24 hours, my ARC peaked out an hour after start, and my Forte seemed to get better day after day after day. Similar differences with other amps I had - the Class A's took a lot longer to settle in than the A/B's.
If your amp has a current inrush limiting (soft start)circuit, then daily on/off should not "stress" components. However, if your lights dim or if you hear a buzzing on start up, then leave it on. That's stress.
The only problems I see with leaving them on all the time is a) it's not a good idea when not at home, and b) the premium on your electric bill if they're Class A.
If your amp has a current inrush limiting (soft start)circuit, then daily on/off should not "stress" components. However, if your lights dim or if you hear a buzzing on start up, then leave it on. That's stress.
The only problems I see with leaving them on all the time is a) it's not a good idea when not at home, and b) the premium on your electric bill if they're Class A.