I think I read some where that you can ask OpenFeint for more OF points if you have an Update.
Yes that's also true. If you have a significant update coming out and you've used all your 1,000 points, they can decide to give you more achievement points if you need them.
But they won't just give you 1,000 more for one achievement if you used all 1,000 on a single achievement. They probably look for that you used the first 1,000 wisely and that your not just abusing the system.