Pay attention to your BP, and he will let you know when it's time to put him back in the enclosure. As long as they are exporing or hanging out, you can assume they aren't too stressed. When they get darty and try to dive into anything that looks like a hide, it's time to put them up. With my Normal guy, I watch his breathing. When he gets uncomfortable with something, his breathing gets heavier. None of mine ball up when stressed, but each of them have their own signs that it's time to go back in the rack.