Carter left office over 43 years ago. He is the president to live longest after leaving office by more than 11 years (#2 was Hoover, who lived nearly 32 years after leaving office; #3 was Ford, who lived nearly 30 years).
Other than those who died in office and those still living, the presidents who died soonest after their terms ended were Polk (103 days), Arthur (1 year and 259 days, and Washington (2 years and 285 days).