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

Funny. I'm old enough to remember when TVs and radios only had tubes. We turned them on and off numerous times and left them on for hours at time. Never remember having a TV  or radio go bad due to a tube failure. Maybe a poor comparison but we are a neurotic group and tend to over think things a bit.

J.Chip

Some of these comments are mistaken.  All gear has an optimal operating temperature; it does not sound better after it reaches that temperature.  

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.