Many tube amps have a stand-by mode in which the output tubes are off but the amp is still warm. My Cary amp have this. When I'm home and know I will be listening that day they stay in standby. When I leave the house or go to bed, everything gets turned off.
I once saw my tube preamp go up in smoke while it was just idling.
I once saw my tube preamp go up in smoke while it was just idling.