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

I leave my gear on 24/7, the only time I turn it off is during thunderstorms or if I'm going away for an extended period. I have a tube preamp with separate power supply it has 4 tubes. The reason I don't turn it off is because I use a big krell amp with it, which would take to long to warm up. I've had the same nos ken rad 6sl7 tubes in it for over 3 years.

@sandemallI also have Don Sach tube preamp and Pass amp. If you leave on your SS, don’t you worry about your preamp tubes blowing while you’re turning it on/off?

@sandemallI also have Don Sach tube preamp and Pass amp. If you leave on your SS, don’t you worry about your preamp tubes blowing while you’re turning it on/off?

I’ve owned tube preamp for 25-30yrs now. Do not worry about your tubes, they will last a lot longer than you think. I use mostly expensive highly sought after vintage tubes in my preamps and in all these yrs, only 1 tube has went bad. I use 20 tubes total in my 3 main preamps. AR SP11 mk 2, Marantz 7 and CJ PV5.  When I’m listening to one of my systems, I turn the preamp on about 12 noon and do not turn it off till 12 midnight.  I have 3 tube testers in house, and like I said, all these yrs, only 1 tube went bad. Whatever system you want to use to “save” your tubes is fine, but the point I’m making, don’t worry about them so much, they’re gonna last a long time in your preamp unless 1 or 2 fails. 

Thanks to everyone for their thoughtful answers. The general gist of things as I summarize your comments in my mind is that common sense should prevail and to turn the preamp off when I'm done for the day, clearly stop worrying about tube life and enjoy the system. The REF 10 does have a 12 volt trigger turn on and off feature as do my Parasound JC1+ amps. This may somehow be audiophile heresy to make use of such a convenient feature, but I love it and with the REF 10 start up mute and delay sequence it seems to work very well.
 I was also asked how I like the new REF 10. I absolutely love it, its less" tubey" than I expected, strikes a great balance between the classic tube and SS sound (so did my Rogue RP7), imaging and depth are great, and I've never had a preamp that didn't seem to change the sound as I changed the volume. I literally get lost as to where I am with the volume level. I will notice that sometimes I am listening at a relatively low or high level without choosing the level numerically, just enjoying the music.
Finally, like many of us, I wonder if I had this or that component would I enjoy my system more. At this point, I don't have any desire to try any other preamp, and that my friends is a wonderful feeling! I hope it lasts!!
Thanks again for the insights!