When they say set aside sufficient time, they aren't just talking the normal 1 or 2 minute cutscenes that are peppered throughout the MSQ. They're warning you that you're going to see a succession of rather significant and involved cutscenes so you shouldn't plan to do anything for a bit longer than normal cutscenes. If they aren't auto-progress on the dialogue then they can't really give a time, since people go through the dialogue at different rates.