At the Div. 1 level it does. You have 5 years from your first competing season to your last (unless you have extentuating circumstances and petition additional eligibility or have a religous exception like BYU's athletes with 2-year missions). There is also an age limit at the D1 level (I believe 25 as a freshman?). I know the rules differ in NAIA schools as I've known runners who have competed at a university for a season and taken a considerable amount of time off and come back to compete at the NAIA level, but not sure of the specifics on their rules. I'm sure you'll get info. on NAIA and D2/3 soon enough. I've also heard of runners who peitioned with the NCAA because they ran a partial semester (maybe 1 or 2 races) at another school and were able to start with a clean slate at a new D1 school, but these are very rare and take a good reason. Hope this helps and good luck to you.