it gives a little boost, but as people previously posted... you need content, links and hard working!
I always register my active sites for 10 years. It's not cheap, but not that much money either as long as I'm not registering a bunch of them at a time. I figure even if there is truly no positive, it certainly doesn't hurt. And it might in fact be a good thing to help with your SERPS. Every little bit helps!