I'm a strong believer in doing things as close to natural as possible. Exposure to light 24 hours a day and excessive heat are the exact opposite. Nighttime darkness is the natural order of things and animals shouldn't have to be terrified the first time they experience it... it should just be a normal routine, it's healthier, their bodies rest, their food is digested and the morning starts a new day. Constant light is stressful, exhausting and they have no concept of appropriate times to sleep or eat.