I loved and even recommended the book, but I think 4 hours would likely be too much for the majority of the people going to see this. Splitting it would have made the movie less climactic in general. Since they seemed to already have the 4 hours it was likely not going to take 3 years for a part 2, but I don't think there would have been much interest in a 2nd movie because just the first half of the plot with an ending in the middle would be a bit lackluster as far as pacing goes. That being said, I would personally watch the 4 hour cut of movie.