I Will Survive — How do ex-presidents continue to thrive and exert political influence? First, they are survivors:

Eliminating presidents who died in office, the first 28 ex-presidents — from George Washington through Lyndon Johnson — lived an average of just 11.6 years after leaving the White House. As of July, however, the Nixon-to-Clinton cohort already averages 15.2 years, a figure growing daily because only Nixon is dead. With Clinton’s brief post-presidency excluded, the mean increases to 17.9 years, and the 54-year-old Clinton may eventually raise the group’s mean post-presidential tenure to twice that of its 28 predecessors. Ford and Carter already rank second and fourth, respectively, in post-presidential longevity. Ford will soon pass legendary ex-president John Adams into third place, and both Ford and Carter may pass Herbert Hoover’s 31-year standard.

Then there’s money, the bully pulpit, bipartisanship, institutional memory… The American Prospect