If it was me, I would stay for all four years, because I'm a giant nerd and I liked having a subscription to the OED and all the other accesses that students have access to. Plus, you know, I enjoyed academia. Not enough to make it a career, but enough to actively dig going to classes.
But if I was stuck at a D1 school where it was basketball all the time all day every day and I was a big deal on campus and all that I'd leave as soon as possible. That's a lot of performance pressure, and I don't have enough time to, you know, actually enjoy learning because I'm stuck playing for a coach who's probably a jerk and for fans who only care about me when we win. Gross. Hide me on an NBA bench somewhere.
Do you think there's more performance pressure at a top D1 school or in the NBA? I would say the NBA (especially since it's so much harder to succeed there). I bet Anthony Bennett is feeling more pressure this year than last.
While I’d definitely would like the money, money isn’t everything. Mo’ money, mo’ problems. Some problems/stress areas that come with being a professional athlete he can put off for another year (which of course he trades for another set of problems/stress he would have to put up for another year as a college athlete).
Not every athlete plays as long as they can, many retire early at a young age (Michael Jordan, Barry Sanders, Rashard Mendenhall) or turn down contract offers in their later years despite being in good health (Reggie Miller, PJ Brown).
Money and fame ain't for everybody.
But I would also probably look at who was drafting at what position. If LA and Boston are in the top 3, that's not a bad situation. But if Milwaukee and Utah have two of the top 3 picks, maybe I go back another year.