Can't find Monkeybean's OP....I can't imagine locking a chicken up like in a dog crate for 21 days. Maybe they don't mind... my 2 went out for at least an hour a day, with the flock, dust bathing, roosting and eating and drinking and I guess pooping. It was harder to manage, making sure they got back on the correct nest, but we did it! No eggs died, and the Momma's really didn't seem to suffer too much weight loss at all. JMHO.
Yes, my hens love having free run. I do lock any hens up I can, simply because the other hens break their eggs. However, when I see them get off the nest I try to let them out to dust bathe and run about. My silkie only gets this a few times while broody, and she LOVES it. I don't think I've ever seen a more relieved, relaxed chicken then a dust bathing broody.