I read something where the world's elite at their respective disciplines need to spend 10,000 hours performing that activity in order to arrive at their skill level. Now, this can't apply to running b/c that would mean somewhere around 80-100K miles, or 20-30 years of high mileage running. On a similar note, how many miles would need to be run before you considered someone a "serious" runner? Here are my 2 cents:
-Novice runner: 0-5k runner
-Amateur runner: 5k-10k miles(5-10 years of 20MPW): has run enough to know the basic principles of training, and through trial and error has by now learned how to minimize injury.
-Veteran runner: 15k-35k miles(10-20 years of 50MPW): has reaped the vast majority of improvements in running economy over the years
-Seasoned runner: beyond