Always turn off tube amps when not in use or near future use. No reason to leave them on they voltage stabilize within mins and with the heaters warm up in 10 mins or less. really not worth the tube wear or power use if not going to be used in the near future. Tube amps have 100's of volts on the plates some are 1000v+ so really do you want that thing on all the time when your not home.
Also don't leave them on when no one is home not really that safe, I've seen tubes self destruct when they fail be nice to be home so you can turn the thing off so not to damage other parts of the amp, or burn your home down. you wouldn't leave your stove on when your not home would you?
I feel its irresponsible to leave equipment on all the time just to say oh I don't like to wait until it warms up. well the planet is warming up so take a few mins to plan ahead when we listen. Turn things on go get a drink hug your spouse your kids what ever then go relax and listen.
if your really savvy get a remote switch to turn them on when your on your way home.