From so many of the posts on here it’s almost like people think that if an athlete is doping it suddenly makes them super human. At it’s essence all EPO does is increase red blood cells making oxygen distribution and use more efficient, boosting endurance beyond what’s normal. Does it prevent an athlete from becoming injured or slow down the aging process? No. Kipchoge is an outlier in this way in so many respects. He has had a world class career that has spanned the good part of 2 decades, rarely if ever has had a serious injury and now in his late 30s has continued to improve on his marathon times. EPO does not have the ability to help an athlete continue to improve as they age. If an athlete has been doping for a long period of time you would still expect their performances to gradually decline as part of the normal aging process. For whatever reason Kipchoge has managed to continue to improve. I believe this is primarily the result of him perfecting his marathon race more and more which has had a net positive impact over any negative impact from aging. I do believe however that Kipchoge will probably not make much more of a dent in his world record. No matter how much of an outlier he is as an athlete Mother Nature will eventually catch up.