What to do in a 20 hour flight?

Watch like 3 or 4 movies, that should take AT LEAST 7 hours, then sleep, let's say u r not a heavy sleeper so 5 hours, then listen to some music 1 hour and eating plus playing nintendo 3 hours. Cam really help anymore. My longest flight is 12 hours, oh, if between swapping planes u have time, remember to recharge ur nintendo