How long should Pre amp (12au7) tubes last in Rogue Preamp?

from the FAQ page on Rogue's website:

How long do the tubes last? 
Preamp tubes and the small tubes in the power amps typically last at least 5000 hours before they need to be replaced. The larger power tubes in the power amplifiers depend somewhat on how hard they are used. "Typical" lifetimes are about 3000 hours which equates to about 3 years if used for a few hours every day.

http://www.rogueaudio.com/FAQ.htm

@aberyclark,
Those new Gold Lion 12AU7 sound amazing. Replaced some new Mullards with GLs and am very happy with what I am hearing, especially the vocals and strings.

I've always heard preamp tubes last up to 10,000 hours.  Are you wanting to change something in the sound or tonal characteristics?  If so, what is it?  

No, just curious. The tubes are fine. I like how they sound...just curious thats all. When it is time to replace, I may try the Gold Lions only because many owners who own the RP-5 say the first thing they do is switch the tubes and talk about a night and day difference over the stock JJ's. 

I've pulled small signal tubes out of 70 year old radios / equipment that were still working. really depends on like others said how hard they are run also the quality of the tube.  IMO, NOS tubes tend to last much longer then their new counterparts but are usually much more expensive so its a trade off.  NOS tend to sound better but not always. New production tubes are getting better every year but also their prices have steadily risen. 

12AU7's are very common so you will never have issues finding them new or NOS so don't worry.