When you edge longer than 4 hours, you're not doing it nonstop witht a constant erection. Most I've interacted with on the subject take small breaks just to stand up, bathroom, smoke, get a snack, etc. Then resume. So the 4 hour erection viagra warning does not apply.
Love to edge for 2-3 hours when I have the time. I always have some intense amazing orgasms when i can edge like that