It should be noted that among recent American marathoners to medal in the Olympics, Frank Shorter was 24 and 28 when he won his medals, Joan Benoit was 27 and Deena Kastor was 31. All had run marathons for years before winning their medals. Kenenisa Bekele was 31 when he made his marathon debut and hasn't run faster since. In hindsight, it certainly seems true Bekele waited too long to make his marathon debut. He appears to have aged out of not only the marathon, but competitive running in general. The last two men's marathon world record holders, Dennis Kimetto and Wilson Kipsang set their records in their early '30s, but they too had years of marathons behind them. While it's too early after only one marathon to say Rupp moved up too late, he probably doesn't have the luxury of 3-4 years running marathons before his skills decline in general.