Someone told me that once a good idea came about it took about 5 years to process it into a book and then it took another 5 years to be accepted by people teaching outside of consultancies.
Of course the other extreme that's taken over the industry is the frontend flavor of the week. Where you learn one in first year, and by the time you graduate it's already been replace (once if not twice over).
Of course, by then, it was antiquated.