I'm with bruteforce. When I need it, I take 800mg several times per day, but only for 2 or 3 days at a time.
The danger in ibuprofen is that a lot of it can negatively effect the stomach lining and cause internal bleeding. Different people can take different amounts and be fine. I can usually take a ton, but my wife cannot take ANY ibuprofen or any other NSAID (like aspirin, naproxin, etc) without it causing gastro-intestinal bleeding. So go slow at first and see how your body reacts.