Doing a little looking around on marathonguide.com last night. I came across a guy at 50-51 during the Fall of 2000 that ran 6 marathons between the dates of 10-01 & 11-19-00 at an average of 2:55:31 over the 7 weeks;1day.
10-01 wineglass 2.59.58
10-08 steamtown 2.55.27
10-15 mohawk hudson 2.53.23
10-29 columbus 2.49.41
11-05 nycity 2.56.42
11-19 philly 2.57.53