Kipchoge and Bekele did have really long careers, but their top notch careers on the track were no more than six years long. Bekele won track medals over a six year span (7 seasons), from 2003 through 2009 (8 gold, 1 silver, 1 bronze, plus World Indoor gold), while his xc medals were over an seven year span, 2001 through 2008, 12 golds and 1 silver). When he shifted to marathon, it was after struggling with speedwork because of achilles issues. His longevity was amazing, winning xc medals in 2001 and running 2:01:41 at Berlin in 2019. Kipchoge won gold over Bekele and El G in 2003 in the 5000m (only three other track medals outdoors, one bronze indoors), two marathon Olympic golds in 2016 and 2021, 18 years after his world outdoor gold, and only one xc medal in U20, when he may have been too old already. But on the track he could only really compete with the best from 2003 through 2007 or so, and achilles issues led him to go to the marathon when he was still young in track years.