What OG, what yeast? Did you use any nutrients?
I'm still in my first cider brew, but I think it's quite common for them to run a lot longer than a beer of the equivalent OG. For one thing, they typically ferment further, and they're lower in nutrients so it can be harder for the yeast to get the job done quickly.
My cider has been going for about a week now and it's still chugging away; I'm going to give it 2.5-3 weeks before racking, I think. The two beers I've done were all but finished in about 4 days, though I gave them 1-2 weeks each.
I wouldn't be surprised if it's still going, based on my limited experience.
