Deborah, this is my first experience with a broody, so I am probably the last person you should ask.
My hen went broody. After 4-5 days, I gave her a few eggs to sit on. I wasn't sure they'd be fertile, as the rooster is quite young, and had only been with the girls a week or so. Anyway, I let her sit on the eggs for 27 days, and none even developed (as a side note, a couple of them *seemed* to be solid when I candled them at the end, but when I broke them open, it was all liquid).
Hen stayed broody.
So, I gave her these 7 eggs, and she sat on them. A couple of my other chickens are very untrustworthy, and I was afraid they'd kill the chicks. I'd separated her part of the coop off with chicken wire, but I didn't do a very good job, and the chickens could still get over anyway. I didn't have a separate place to put the broody hen, and I was afraid if I moved her into the house, it would break her.
When the eggs started to pip, I moved them in to the incubator.
She's still out there on the nest, with an egg that I was pretty sure is no good, and we're at day 23. So, she's basically been on this nest for two months. She gets off to eat and drink, but she's lost quite a bit of weight, poor thing. The other chickens don't seem to recognize her either.
I'm going to try to get her off the nest today.