It's almost more like singing than speaking. When I teach it to actors, I start with having them sing a speech, and then making it progressively more like spoken words. Singing naturally encourages a smooth, constant flow of air, rather than the choppy way you naturally speak.
That said, the more tired you get, the harder it is to do that. You start straining your muscles, and your vocal cords start slamming together. For singers, who do this a lot, it eventually causes scarring, and it can end your career.
I don't think I could do 25 hours. And Booker is going to be out of commission for days -- he literally shouldn't talk for a week. He may just have learned all this by intuition and example rather than training, but either way, it's gonna rip him up.
