Is it wrong to leave my amplifier on all the time

Some folks will say that cycling on and off stresses the caps more than leaving an amp on all the time. I think you're fine either way really.

I left my Class A/B amp on most of the time over 20 years and never had a problem, and I’d only turn it off if I was leaving the house for more than a couple days.  The impact on the electric bill was minimal, and it was really nice having the system warmed up and ready to go whenever I got the urge to listen.  If possible talk to the manufacturer and see what they recommend. 

Some say, leave it on.  Some say, power it down.  Many years ago, I asked myself the same question and needed a definitive answer to the question.  So, I asked the experts, the amp manufacturers.  I was advised by the manufactures that it was perfectly ok to turn my amps on and off as many times during the day as I wished  and doing so wouldn't harm the amps one bit.  Personally, I always power down my amp when it's not going to be in use for a prolonged period of time.  Happy listening.  

In other discussions,  you mention a Sugden class A amplifier.  They run hot which might impact longevity. Check with manufacturer. 

Either/or...

Just don't turn it off and then immediately on again without waiting 3-5 minutes.

DeKay

I've had a few power amps that don't even have an on/off switch. Just left em on 24/7. No harm at all. But I wouldn't worry about it either way.