Agrees.I'd almost forgotten until aart mentioned adding extra straw around the heating pad on really cold nights - I throw a folded wool blanket over the heating pad when it was to get down below freezing. That tends to focus more heat downward to where the chicks are.
As for 24/7 light, one of the biggest benefits of the heating pad is the absence of light. Again, the broody hen analogy - she has no running lights that go on at night so the chicks can pig out all night on food. They don't need to eat at night. They quickly establish a day/night rhythm and they fall into a pattern of eating all they require during the daylight hours and they sleep all night. This is nature's way.