I don't think it's all that impressive. For comparison the fastest known time for the Appalachian Trail is 41 days, 7 hours, 39 minutes by an ultra runner. That's 2,190 miles up and down mountains. Averaging 2 marathons a day with 11,000 feet of elevation gain/loss each day.
I bet that guy would have no problem cranking out 150 marathons in a row if he was interested.