You can take up to 4 grams, or 4000 mg a day of tylenol, that's limit usually prescribed in the hospital (I am an RN). We give 650 mg of tylenol every 4-6 hours as needed. However, I don't know for how many days in a row...
Never taken Darvon. Percocet makes me itch like crazy. We get Darvocet for people who are allergic to Percocet.