How long do tubes in preamp last.......

I am thinking about a tubed preamp. Unfortunately my wife will have access to the system. She has never turned off a light and opens the windows in the winter instead of turning down the furnace. I cannot expect her to turn off the sound system. I know a pre's tubes last longer than an amps, but what are the ups and downs of leaving the pre on for long periods of time? thanks......
Preamp tubes usually last A LOT longer than tubes used in an amp. A rough estimate is 10 times as long. It all depends on the tubes and preamp. What preamp do you have? What tubes does it use?

I have owned a Croft Vitale pre-amp and currently use a VTL 2.5 pre-amp and an Audio Research PH-3 phono stage. I have left them all on all the time with no problem, as recommended.
If you can "mute" the preamp when it's not in use you can extend the tube life even more. The tubes in my preamps have lasted at least 2 years( an average)