That depends; who are you? If you were a past college football player who wants to return after playing four years, sorry, but you cannot return to play college football after your 4 years of eligibility are up.
You can play college football as long as you are in college. You may also be "Redshirted" Which means you are removed from the roster and cannot play, But you still can play your four years after the redshirt is up. In short, 4 years.
In college football, "The Death Penalty" is a term used when the NCAA rules that a University must discontinue playing intercollegiate football for one or more years. It happened a few years back with Southern Methodist University.