They don't need light, I would think they'd do better with a regular day and night schedule actually, but they do need heat. Since we use light bulbs to provide heat it does have to stay on 24/7 until they no longer need heat. Then I usually start out turning it off for a few hours during the day and steadily increase the time until it's off all day and night. Most of mine I removed the light sometime during the 3rd week but I keep my house pretty warm in the summer. Watch the chicks. If they are huddled together near the light they still need it. If they start scattering about or sleeping away from it you can start lessening the heat by raising the light or putting in a lower wattage bulb until they are ready for you to start turning it off.