MINNEAPOLIS — The end is coming for Bill Belichick, and maybe the last great trick of his unbelievable career is that people don’t see this. Belichick will turn 66 this spring. He is essentially doing two jobs that are more than full-time: Patriots’ head coach and general manager, though he does not officially have the latter title. He has never taken a year off. Logic says he cannot do this at this level into his 70s, and Belichick has said that himself in the past. Well, 66 is not so far from 70. You don’t need a degree from Wesleyan to do that math.