When Johnny officially retired from adventuring at age 55, the reason given was his age and his desire to be with his wife and children. The real reason was similar, but more severe. Johnny wanted to spend his last few months with those closest to him. And away from Reed.
Ben had died 10 years earlier. Reed knew the radiation was going to continue to effect their physiological states. Reed had worked out the math about 3 hours after they initially crashed.
Johnny wanted to be away from all of that sadness, if only for his last few years. Susan was rarely around anyway. Franklin and Valerie were off doing lord-knows-what, and Reed never cared much for people. Susan just took too long to learn that lesson.
Ben, his big sister Susie, Cancer, and Reed was the cause of all of it. Him and his big brain. He got Ben to throw away his life and career to pilot that rocket. And what’s worse, Reed knew the radiation was out there. He just always seemed to care more about his test tubes than his family.
Poor, poor Ben. He died at only 42 years of age. His heart was too heavy. He was made of rock, inside and out. And Ben’s heart had a bigger job than anyone’s. It could not handle it.
Susie said Reed silently stared at Ben’s headstone for about 2 hours. She said she had never seen him so stunned, and that it was what he needed.
Reed still lives in the Baxter Building. Susan is with Namor and she has never been happier. Johnny died shortly after Ben’s funeral. Turned out that Johnny’s flame was generated by some part of Johnny that was finite. When he burnt through the fuel, he started to get sick.
Susan’s powers had left her blind, and after 4 rounds of radiation therapy, “remission” was good enough. She can no longer see, and she has never felt better in her life.
Reed’s struggles with his ongoing physiological changes have not been heard of. Many of his research assistants have stated that he frequently wears a suit of powered armor, like Iron Man.