The way to break in any component is to use it as you normally would. That means cycling the power. Leaving equipment on for 100's of hours at a time doesn't help. Just use it and enjoy it.
Amp burn-in..Best technique
I will soon be getting my new Mcintosh MC591's. I am curious,......does it matter how loud you play? If I run a CD on continuous repeat,...does it matter if I turn it way down? Or does that not offer enough resistance/load to drive to have a "break-in" effect. My wife would not be happy if I had my system playing at high levels all day.