I oil pulled for 5 1/2 hours straight once, while on a long drive from one state to another. Never had any adverse reactions from it, though the large paper cup I was using to spit in during the drive was really gross by the time I finished my trip. And I've done several back-to-back sessions, as has Trapper. Trapper has said something about getting a sense of euphoria after 5 back-to-back sessions.