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

IME, my Rogue preamp was easy on tubes (12au7’s). The tubes in my Perseous Magnum lasted for years.
There is a difference in the quality and longevity of tubes based on the dealer you buy from. Only two tubes died and they were not purchased from a reputable dealer.

I'm no expert but I always thought driver tubes are not run very hard and should last like two or even three times as long when compared to the amp's output tubes (which run anywhere from 2000 to 6000 hours depending on how hard you drive them and their bias setting).

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?