rule of thumb: how long do you leave a tube preamp on versus turning it off then back on?

I don’t have an answer to OP’s actual question, but I thought I would restate it since so far most have answered other questions instead of what they asked.

What duration of time left on is equivalent to the wear of start up for tubes?

If you leave the room for 5 minutes it clearly makes sense to leave your tube equipment on. However, if you are done for the night and going to bed and probably won’t be using your tube equipment for 12 hours it makes sense to shut it down. What about the times in between? Most days I can listen for a little while in the late afternoon and then again late at night. For that average 2 hour gap I wonder exactly what OP asked. Do I leave it on or shut it down? I usually turn off tubes but leave on SS. I’m sure it would be heavily tube and equipment dependent. Some tube types are more tolerant to startup and some equipment is kinder.

For that average 2 hour gap I wonder exactly what OP asked. Do I leave it on or shut it down? I usually turn off tubes but leave on SS. I’m sure it would be heavily tube and equipment dependent. Some tube types are more tolerant to startup and some equipment is kinder.

That’s why it’s always best to call the amp’s manufacturer and talk with them about your listening habits and get their advice as to when to leave it on or turn it off. What somebody on Audiogon might have done doesn’t really help much.

Keep mine on for about 15 to 30 minutes, prior to listening....its a tavish phono preamp with small tubes of the 12ax7/12au7/5751 variety. These tubes have a much longer life span than the larger power amp tubes. I will usually turn off preamp soon after listening, although I sometimes procrastinate and its left on for an extended period of time, not too worried. 

sewolla

... When I am done with my listening session, I turn it off, pre amp first, then the power amp.  When starting it up, I reverse that sequence and first turn on the amp. Then the pre amp ... and am careful to make sure the same start-up and shut-down sequence is consistently followed.

The best practice is to do just the opposite. If you turn on your preamp first, any noise it might send to the amplifier won't matter, because the amp is turned off. Otherwise, the amp could amplify any turn-on transient. The same applies in reverse - if you power off your amplifier first, any transient that might occur when you turn off the preamp won't be amplified. I realize you're not having any problems in your system, but you might want to rethink your practice anyway.

When I’m done listening for the day, everything goes off and goes back on an hour before for warm up.

all the best.

JD