Some new research has concluded that staying up past midnight can be harmful in the long run.
Mass General Hospital in Boston found that staying up later can result in increased drug and alcohol use, and higher food intake. Apparently the brain is pre-programmed to sleep at night and be awake during the day. If the brain is asked to stay up later, it doesn’t get enough time to heal and recover.
There are exceptions though. Some “night owls” are more creative and productive at night.