Family physician:
It's entirely dependent on the individual. Generally, when we talk about recommended maximum dosage of NSAIDs, we recommend Ibuprofen 400mg three times a day (or 1200mg daily). Some circumstances (pericarditis etc) may require higher doses than this but 600mg twice daily is certainly high dosage.
NSAIDs, as posts have alluded to, have a host of health problems associated with them. They inhibit the ability of your stomach to protect itself from acid (potentially leading to ulcers), they increase the likelihood of thrombotic events (stroke, heart attack etc), and can predispose individuals to acute kidney injury.
With that all being said, if you are a YOUNG (