Dude, please do yourself a favor and go out and by Sports Gene by David Epstein.
The NCAA has changed the rule since then.
If at the HS gradudation, you don't go to college, your clock starts ticking one year after HS graduation. So pretty much the oldest anyone could be is six years out of college unless they are Mormon/Military as explained here on page 147:
http://www.ncaapublications.com/productdownloads/D114.pdf