i have both main lights & night lights in my loft ,only use the main when need to tend to birds when insufficient daylight....but use night lights in breeding section they are on a timer from around 1630/1700 to 0800/0830hrs...find it enables y/bs to be fed by parent birds that bit longer & also prevents squabs from getting chilled if hen comes off nest for any reason & able to find way back ....just how i do it & works for me ,others use different ways & works for them ( rightly so),
try different ways & adapt method which suits ,dependent on when pair up etc ,work commitments etc