I'm not sure about running specifically (nor this mapping of 5 hours to 30 miles, since depending on your capability as a runner, 5 hours could mean 50+ miles), but cyclists, x-country skiers, triathletes[0] etc rack up more than 5 hours a week, and they are the ones with the massive VO2 maxes, in comparison to the runners who have to suffer from the mechanical impact of running.
[0] as a former wanna-be triathlete, I'd run 2x2 hours a week, swim 2x2 hours a week, cycle 2x5 hours a week. That's probably minimal to be able to complete an ironman, and I'm sure the sub 9 hour folks are putting in twice that, which would be 18 hours[1] to 36 hours of training a week.
[1] that's why I stopped; I figure I can spend about 10-12 hours a week on "fun" exercise including social stuff. Triathlon training on the other hand is very solo intensive.
