I've never read the book. Only seen the film. How would it turn out in the third-part? What material would they use, if you don't mind me asking? Really? In the book, Mr. Perlman dies in the 20 years fast-forward. They didn't show that in the film; rightfully, so. They just left it at the speech he gives his 17 year old son. IMDb says there's a slated sequel. To show realism. These are realistic aspects throughout the film. Just like the guy who breaks his leg, mid-climbing up a roped ladder. Having an urge to crap, tripping, breaking a finger, are minute details that happen in real-life. Nolan was trying to capture every detail.