The only reason the ibuprofen bottle says "see a doctor if pain persists" (or equivalent) is that, in general, if whatever you started taking it for still hurts then there's something going on that you should have a doctor look at. It's not because there's a medical reason why it's not suitable for extended use at the OTC dosage. My doc had me on 1200mg daily for three months before the side effects got to be too much....