My experience is different. I`ve had hens set long enough to hatch 3 cluthes of eggs and then try to hatch rocks, but with no ill effects. They always come off the nest when they need to and, when setting, are in sort of a trans that slows all body funtions. One or two, or even three days without food, water, or eliminations, doesn`t seem to hurt them. There may be exceptions and probably are, but in almost 54 years, I`ve never had a hen suffer any ill effects from setting too long. Also, the surest way to tell if a hen is broody is when she refuses to leave the nest at night to roost. Some hens give it up after a day or two, but most of the time (99.9%) if they are on the nest for 2 nights, they will stay. I see fordmommy`s experience is different and there is no sure thing. Just sharing what I`ve seen in my lifetime........Pop