I used to just free range them when I was home, but eventually I got the courage to let them out when I was gone. They tend to hang out all day under bushes and in a brushy area near the edge of the yard. The rooster is very protective when he sees danger and they are good at scattering and hiding if something does come around. Now I let them out early in the morning and lock them up when I get home at dark. I did build an automatic pop door opener/closer, in case I get home too late. I look at it this way, they have a much better quality of life roaming around and hanging out dust batheing under bushes than if I lock them in a coop/run all day. If something were to happen, (knock on wood it doesn't), I would be sad, but at least I know they had a great chicken life. The only chickens I have lost have been when something broke into my coop at night and killed a hen. That was worse because they can't get away or see in the dark and it's my job to provide safety at night when they are most vulnerable. You have to decide for yourself whether it's worth the risk or not. I think the risk is fairly low for me, but that's not always the case for others.
Lisa