Just thought I would share this excellent example of pacing at the NYC Marathon on Sunday, by one of my athletes. Yes, he slows down late, but never falls apart, because he was patient and executed the correct pace early on. (Click on image to enlarge).
You'll notice only an 11 second difference between his fastest mile, and his slowest mile, on a course known for having some hills, plus wind.
You must be patient in the marathon, because even being patient will bring challenges late in the race.