It's easy... Let's just wait for the game to come out, and see how many people tell us they fell asleep while playing the game. If there are none, it probably means the cutscenes aren't too long...
I mean, I sometimes fall asleep during movies, I'm pretty sure it would be much easier to fall asleep with a game cutscene.
My Mario Kart Wii friend code: 2707-1866-0957