They all retired at age 38. As did Fran Tarkenton. Dan Fouts retired at 36. Staubach at 37. Unitas made it to 40. In the modern era, the only great to go the distance was Favre...41. Brady will be 37 when his current contract ends. How will Belichick ,the practical economist and NFL historian, move forward in 2014? My memory is a little foggy when it comes to remembering why these legends left the league. Marino lost any remaining mobility. How about the others?