The question now was not so much whether Makau could sustain the pace, but rather whether that surge would cost him? He had built up such a buffer that he could afford to run the final 10km in 29:49, which was much slower than anything they'd been producing up to that point.
The answer was that he would pay for the early pace, but only a little. His final 5km segment, from 35 to 40km was easily the slowest of his race, but it was still 14:59. Compare Makau's line to that of Gebrselassie, who built from halfway to get faster and faster when he broke 2:04 in 2008. Makau's graph is "going the wrong" way, but not quickly enough to save the record.
As always, attention will now turn to the limits for marathon running and people will start talking about sub-2 hour clockings. That's a little premature - if each record lasts say 3 years (because weather and pacing can undermine even the most gifted athlete), and if the times improve by around 20 seconds per record, we'll be commenting on another eleven world records and will be waiting until 2044 for that to happen. If it happens at all. That kind of speculation is always fun though.