I don't know why any college coach would go to the NBA anymore unless it's a fat garunteed contract and even then I would have my doubts. Name the last guy to jump from college that held an NBA job for an extended period of time.
The shelf life of a NBA coach is short these days. Name guys that have been with their teams for 5 or more years. I think Jerry Sloan is the longest tenured. After that I think it's Gregg Popovich. Lawrence Frank since 2004. Phil Jackson took a year off so he's only been with the Lakers since 2005 in his current stint. After that I really can't name you anyone that has been with their team for more than maybe 3 years? Mike Brown and Flip Saunders were hired in 2005 tooHere's the list of current coaches:
NBA.com: Coaches I was trying to google for a list of current coaching tenures but can't find anything recent. Most teams have changed coaches in the past 3 years though and anymore even making the playoffs is not enough to keep your job.