I think everyone could help answer you question better if they knew what the estimated FG was supposed to be. If the FG estimate is 1.008 then I would say wait. If the estimated FG is 1.029 then go ahead and keg it. Either way waiting 2 weeks will help the beer.
Is there any activity in the airlock? Did you have any trouble with the smack-pack/starter/dry yeast? What is your fermentation temp?
My yeast sit at about 70F, and they usually go from 1.055ish to 1.010 after 7 days.
Since your gravity is still that high, my guess is that you may need to add more yeast. Either that, or you have a ton of unfermentables, like starches, in your wort. That would mean there's nothing left for the yeast to eat and you should rack it.
I don't know much about low temps during fermentation, since I don't get them.
No Fridge = No Lager = Me sad
its 71 in the room and I used muntons dry yeast.I made a starter and it bloomed fine.T his was my ftrst batch ever and I'M pretty sure the wort was above 80 when i added the yeast,rookie mistake.Besides that it tases fine.
Seeing as how my ground water is like 70 year round, I pitch in the low 80s everytime. I haven't had a problem with stillborn yeast thank goodness. The only dry yeast I've used is Safale, and I know different strains attenuate to different FGs. I still need to get a prechiller to bring the initial temp down though.
An FG of 1.015 is pretty much done. You might be able to sweak some more out of it, but I wouldn't worry until your next batch. I do suggest waiting a couple more weeks to really start draining it. You'll notice the flavor changes.