my thought is . . . they are MY CHICKENS.
I have taken on the responsibility of taking care of these animals that have been taken out of the wild and had many of their wild traits breed out of them and now they depend on me to intervene for them. While I try to allow them their leftover wild nature I realize that some breeds may not have the natural instinct and speed of their ancestors.
I let them out when I am at home, or when I have a quick couple trips during the day. I do not feel comfortable letting them be exposed all day if I am not home. If a predator came, I could come out and shoot it, and maybe lose 1 or two, the price I am willing to pay to let them freerange. But if I were gone all day, something could spend hours tracking them all down and killing them. In my yard and nearby it is alllllll field, very few trees and bushes and not good for chickens to hide from predators. Some of you may have different terrain, so it may not be an issue for you.
Build a large enough run that you don't have to feel guilty for not letting them out. And then let them out when you are comfortable. But be aware that a predator could come at any time. life in general is a risk. So add in the breed you have and it's habits and your terrain and known predator patterns and judge by that. Obviously, it would be preferable to let them run all the time, but I think for most people they would just be feeding coyotes.