My chickens free range all day and every day over 6 fields. I have been lucky so far and apart from one problem (?fox ?rooster injury) have not had anything untoward happen. At the moment I have 8 week old chicks who have just started to go out, but, as my big boys know I feed the chicks often, they hang around the back door with the chicks. (I am very lucky in that the huge Brahma boys let the chicks feed from under their feet).We are a good distance from a minor road.
We have buzzards and kites overhead, but they do not venture by the house. Ravens and other crows are potential problems, but our Border Collie delights in seeing them off the premises.
I acknowledge that the strategy may be rather risky, but the particular dynamics that prevail seem to have rendered the environment relatively safe.
We also have a cat and a goat. the cat helps to deter fling predators and the goat smell keeps the foxes away (In fact the smell is enough to keep anything away).
I think that the decision to allow free ranging depends upon what potential predators there are and what you can do to lessen the risk from those predators. No doubt that the birds love the freedom. Oh, and never have to clip their wings, the Brahmas are just too heavy to fly and the others know how easy it is for them to get their food. Having the power of flight is useful if there are any prowlers,
Sandie