Do I NEVER shut it off…?

Yes and yes. People have the perception that heat is the enemy of electronics. They are only partially correct. The enemy of electronics is the heating and cooling cycles. This creates the expansion snd contraction of electronic components that will creat micro cracks and eventually lead to failure. Quality manufactures use components that are made for their heat ratings. I am running an old sansui 7070 in my wife's business. Other than power outings it has not been shut off for 26 years. I run class A mono blocks and yes they get very warm. When I am done listening I put a box fan on them. Don’t feed into the so called “green” crowd. Each on of my amps running all year costs less than their idle Prius charger hanging on the wall costs them for one month.