What did paul say he learned that night? what does this mean? the green mile

Paul Edgecombe was a correctional officer in charge of the death row inmates at the Cold Mountain Penitentiary in The Green Mile. He is portrayed by Tom Hanks, while Dabbs Greer portrays the old Paul Edgecombe. 
He was 40 years old when the events surrounding The Green Mile happened.He begins to tell the story about John Coffey and his execution to his friend when he was 104 years old and despite his age he still looked very alive. Even the mouse Mr. Jingles, that he had taken care of since then had outlived his time and continued to live with Paul. In time he realized, that those cured by John Coffey additionally have an expanded lifespan, which forced him to see his wife and children die before him. He later is forced to see his friend die and be at her funeral, too, which forces him to think, how many years he will still have to live until he dies, too.