Do you leave your components on 24/7?

I leave everything on standby that is solid state, but not the pure class A Threshold T-200 - it takes about 20 minutes to warm up and start to sound good. The outboard power supply of my Threshold DAC-2 runs extremely hot, but I leave it on anyway since the manual recommends it - and there is a noticeable difference after it's been on for about 72 hours.

Never. I turn everything off.

Yes, unless I'm going on vacation.

My gear seems to sound great after 20-30 minutes. This includes tube and solid state. None of my gear sounds bad enough so I can't enjoy it while it's warming up.

Standby switches could be for different reasons. On a remote controlled unit such as a CD player, remote preamp, a standby switch may shut the remote receiver section of the unit off, that is normally needed to receive the remotes signal. On a lot of tube gear, the standby switch shuts of the B+, that feeds the higher operating voltage to the tubes. The filaments would stay on in this type of example, to keep the tubes warm, without the the wear, and extra electric needed. This is just a couple of examples. The purpose of this post is, even when you have a unit in standby (typically SS), the main audio part may be shut down, and cold. These examples aren't always the case.