I would not use it on a bet. I do not want to be constantly pumping insecticides into the air, and onto the ground and items my chickens are eating, and onto the chickens themselves, for relatively little reason. Especially since I eat the eggs.
In horse/cattle barns at least there is the justification that with large numbers of large livestock it is real hard to avoid a considerable plague of biting flies that can greatly distress the horses cattle etc. (Though I *still* do not like auto fly spray systems in horse barns [no opinion on cattle], because, again, I do not want that much insecticide going into my horses and their buckets, feed bins, etc].
A backyard chicken coop, though, is not going to get ANYthing like as fly-ey as a large-livestock barn, not if you are managing it even halfway right. Keep the run DRY and picked-up, hang some flypaper in the coop out of chickens' reach (and where you won't whop into it with your head!
), and there will be very few flies. Certainly not enough to, IMO, warrant spraying chemicals around multiple times a day on a timer's say-so.
JMHO, I realize that people who have more faith that pesticide manufacturers prioritize human health above profits, and less awareness of toxicological studies that have been done, may disagree with this type viewpoint,
Pat