You're misinformed. The elite Kenyans are running tempos 35-40k at or within 10% of altitude converted marathon pace (for Kipsang, Mutai, and Kimeto, that was also WR pace). Wanjiru is quoted saying he did regular 30 mile runs. Maybe the Americans have it wrong...??? The Kenyans also do a ridiculous amount of interval work in training for a marathon. Up to 25-30k worth of work. Meanwhile, Americans who go out and disappoint in every major marathon, think that 5x2 miles and 15 mile tempo runs are the way to go. What was it that Mutai said his camp was doing, like 150 miles per week in their heaviest load?? Not because that's a magic number, but because that's just how much they end up with when they are hitting the workouts they need.