It's a very interesting and informative thread. Here's one representative passage that Leon quotes from sources:
"Atsushi Sato of Japan, who finished fourth at the Lake Biwa Marathon (the oldest marathon in Japan) this year in a time of 2:08:36, reportedly covered 2500 KM in the two months leading up to the marathon. That is 1,553 miles. That averages out to 776 miles a month / 195 miles per week / 27.8 miles per day."