What may differ are certain wrinkles. The play calling is going to shift based on opponent (what the defense gives you), the situation in the game (time, score, etc), the situation on the field (field position), etc. I think you're mostly correct though, it's not like we are hiding Tom Brady and the Patriot's playbook in the locker room somewhere. Granted, big time games are the perfect time to throw something out there that's meant to be used only once (i.e. the Boise State weird statue of liberty type play in that bowl game...or the fake punt in the ACC championship game last year). We MAY see a few plays we've been saving as momentum changers, but I highly doubt that number is more than 2 or 3.