Mine hatch outside and raise chicks well into October. Usually a predator gets the eggs and the hen gets away, which would mean you lose the eggs. If there is a predator.
Extreme care must be given to moving a broody hen as there is a good chance they will abandon the eggs. They pick out a good safe place, and usually consider any spot you move them to as substandard. The biggest threat to the success of a broody hen is other chickens, that is why they pick a spot off the beaten path.
If you are set on moving them, you need to put a five gallon bucket in their spot, with nesting materials and their eggs in it. Do this at night and then leave them alone until she settles in the new nest. After a couple days, if she is still on the nest, you can put a lid on it and move her at night. She has a much better chance of staying on the eggs if she is still in her bucket. You need to have a decent sized enclosure to move her to, free from other chickens. All moving must be done at night, once she settles on her still warm eggs, most will accept what you did. You can't change too many things at once. For instance, you can't move them to a new nest, with a new location with different eggs all in one move. It can be done, but must be done in stages.
The way it works, a hen lays an egg in a nest, one a day for ten or more days. If she accumulates enough to set on, it is out of the path of predators. Most predators will be drawn to the rest of the flock, and the food that they might have left over.
