LOUISVILLE, Ky., Nov. 10 — It’s been 80 years since Robley Rex served in the military, but he still lives like a man on a mission. The 102-year-old Rex — Kentucky’s oldest known veteran — spends his days at the VA Medical Center in Louisville, not as a patient but as a dedicated volunteer.HIS FAILING EARS don’t hear the many “thanks” directed his way as he makes his way around the hospital aided by a walker. Still, he carries on.