It depends who you ask. The recommended maximum dosage of acetaminophen ranges from 3000-4000 mg /day, so you are probably OK with what you are taking. If you have any concerns about liver damage you can get routine blood tests for that. Don't know what your med insurance situation is like but if you've got decent coverage, just ask your primary care physician for an ALT/AST order to take to LabCorp or anywhere to check liver function.
The other thing I'll mention is that liver damage from acetaminophen comes from a metabolite, not APAP itself. Take 200-400 mg Tagamet orally when you plug, this will help to block the conversion to the metabolite and decrease the liver-damaging metabolite concentration.