It's really interesting that you bring up time like that, because one of the things that's really hindered me in school is that as a kid I was such a fast reader that I never learned how to put a book down and pick it back up later. If I can't read it in one sitting, I'm not interested, and it's really hard for me to wrench myself out of a mindset and come back to it some other time. Mind you, I consider anything under 4 hours to be "one sitting," and for me that covers books up to about 450 pages long, depending on how dense they are, but still.