At least two weeks WarescotFarm, sometimes three or more. This is the reason people break broodies as fast as possible. It takes a lot out of the hens as well. We've put ours daytime only in a large cage with a 12mm mesh bottom standing on logs. Most one has done is 2 weeks, several only lasted one or two days. Clip-on feeder and drinker then nest boxes blocked at night so she has to sleep on the floor or a perch. We have stopped leaving them out overnight when one died earlier in the year.