I take a 10 hour transatlantic over night flight every year. The flight leaves LAX around 8pm and arrives in Europe approx 1pm local time the following day.
The flight is on day time for about the first 3 hours, bright cabin lights, people moving around, cabin crew serving drinks, then the full meal and then the clearup. After the clearup, the flight then goes to night time, cabin lights are dimmed, window blinds are down and the noise level quietens down and there is less movement.
During the night time part of the flight, most people try to sleep. BUT its not mandatory. Everyone does their own thing. Some people walk up and down the plane all night, some people turn on their over head light, some people watch movies, some people read etc etc.
About 2 hours before landing time, the main cabin lights are turned back on and its now morning time. The cabin crew will now serve breakfast and people wake up. The noise level increases and people start to move about in preparation for landing.
On these flights I usually have a neck pillow and once the main meal has been cleared and the cabin lights dimmed I try to sleep. I usually put on the inflight entertainment either films or music and just relax. I usually just have 1 alcohol drink with the main meal. I buy a large bottle of water at the airport before the flight and keep this in the seat pocket. I usually try to pre book an aisle seat. If I have a seat mate, I try to talk to them during the day time part, so that at the night time part they are comfortable asking me to move to let them out for the restroom. I always tell my seat mate thats its ok to disturb me if they need the rest room.
