I let my chicks tell me when they don't need the heat light, I would move it up until they are comfy,(or lessen wattage on the light) I would be more apt to use at night longer then day, if they are in a temp controlled house they will need it a lot less then if they are in brooder outside. The first chicks I had I had done all the reading and knew it was 5 degrees less per week for weeks, my poor chicks I was sooooo by the book, but then I had a broody mom and chicks and saw they didn't freeze to death and die if they weren't heated for more then 2 minutes that opened my eyes on chicks for sure. I was so bad I wouldn't even take them out from the light and hold them aftaid they minute or two they weren't under the light would kill them! lol