I lock ours up at night as a rule. However there are times when we are not home until after dark. Especially in the winter when it is dark at 4 pm! Closing the coop is always on my mind as the sun starts to set, unless my dogs are out. Well, its still on my mind, but I calm down a bit! As soon as we pull in the yard I am jumping out of the pickup and shutting the coop.
During the summer we like to go camping. We just leave the dogs out to guard them. The first few times I would worry all weekend, and hold my breath as we pulled into the yard. We have not lost a one to a predator yet. I know this is tempting fate and could happen. But so far this has worked for us.
They are in an enclosed run with hardware cloth buried. That won't keep out something small(weasel?) or something that can climb the fence though.