I believe that getting up in the middle of the night and getting extra done is perfectly normal.
There are those that work about 2000 hours a year, say 40 hours a week for about 50 weeks a year. Then there are those that do more and many of those who strive for success and those that achieve success get the extra done while others sleep.
This extra can relate to many things like extra work but for some of it may be exercise, volunteering or research.
There are so many examples of how you can find more hours to achieve more and looking at the extra hours.
Some people make it a routine to start their day really early, get 3 or 4 hours in before everyone else, some do the opposite and stay late, and for me, it was always random. When my brain is awake and spinning, I simply get up and do something about it and for as long as it takes.
Some people say they get their best ideas in the middle of the night, and I believe that too.
So if you want to achieve more, find ways to do more and finding extra hours when everyone else is asleep I think is perfect.