Myles,
During the weekend, I tend to practice in hour spurts. I turn the amp on (Fender Hot Rod Deluxe), let it warm up for 10 minutes then practice for an hour.
Then, real life takes me away for awhile. Once that's done, I do it all over again... turning on the amp, letting it warm up... etc.
I can do this anywhere between 4 and 5 times on a given weekend day.
Am I hurting the amp by turning it off/on in this manner? Should I just leave it running longer (in standby mode) for the time I'm away (if it's not too long like leaving the house etc)?