My chicks aren't even 1 week old yet, so I am still learning. So far, I leave my light on all the time, but it is on a pully system, so I can raise it higher during the day (when it's warm here in Central FL) and lower it at night so it's warmer. I also have a digital temp gadge in there so I can see how warm it is from my house, and adjust the height as needed. My husband is so smart, all his ideas. I check on them regularly and they seem to sleep just fine with the light on. I use a heat light with a reflector, it's a good sized brooder.