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

Many years!

I would contact Rogue Audio and ask them how long you can expect the tubes to last in your preamp. They should be able to give you average life expectancy of the tubes they decided to use in their preamps.

It also depends on how many hours you are using the preamp on a daily, or weekly basis of course.

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?  

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. 

Tubes are not exact as two identical units may be totally different.  Your ears and an occasional tube testing will let you know.  

Nos Mullards or telefunkens will last as long as you own your equipment. I’ve got some from the 50s and 60s that still test 90%. They must have at least 20 k hours on them. Obviously mine are not nos but I’d feel real comfortable paying good mo eye for them from Brent Jesse or another reputable tube seller. 

Gold Lions sound really good to my ears. They should last a good longtime in the Rogue

I haven't tried the Gold Lions yet, but I put a pair of NOS Tung-Sol tubes in the preamp section of my Rogue integrated amp and was surprised at how much better it sounded.  I'm sure my JJ's were still fine after a few years but it seemed like a cheap enough experiment and it paid off.

Usually 5000 to 10000 hours if the tubes are not defective. 

Thanks for the info. I may purchase a set of Gold Lions sooner rather than later so I have working back up tubes.

I think replacing the tubes prior to a need to do so is a good idea. Having a backup set is handy and you may rediscover your preamp.