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

Yes, thank you for reframing my exact question! I think no one may actually know the answer because there are too many variables for a "rule of thumb" guideline. Lots of well intentioned responses. I'm going to turn it on a little before or concurrent with my listening, and leave it on the rest of the day, turn it off when I head to bed. Done! I'm over it!! Thanks!

Thank you both. I'm over thinking it as just after I purchased my REF 10 I saw the forum comments here a couple days ago about ARC equipment blowing tubes, and the further comments about how the guy couldn't
get it to be reliable. So he felt he needed to go to a Pass preamp. That is just the kind of story that gets my over worrying mind busy!!

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!

Thank you for reminding me! I have known that most damage to electronics is caused by the cycling of being turned on and off. I will be doing power cord and interconnect shootouts and I'll be sure to be careful not to cycle it on and off. I used to leave all my solid state gear on all the time, but a few years back we had a voltage surge and it damaged my Wadia 16, three TVs, two sound bars and several other electronic items. Now I'm careful about turning my system off each night. I did install a Leviton whole house surge protector at my panel and I do have everything but my SS monoblocks plugged into a Shunyata Hydra Delta 6 which theoretically has surge protection, but factory claims about "FULL" protection are unclear to me.