Fortunately I have only been asked, not required, to lower window shades on all my redeyes. It really depends, and I know I am getting off-topic here. On long flights from Asia to the US that depart late at night for example, it is best to take a short nap very early in the flight then stay up the rest of the flight so when one arrives in the evening in the US, they are tired enough to go to bed and sleep soundly. Everyone who slept half the flight will have a much harder time with jet lag. The main reason I choose a window on such flights is so I can control the window shade. I lower it half way but having natural light helps in several ways to overcome jet lag.