Decades? I don't know who wrote that, but Ben Franklin was was not alive "decades" after they served together in France. He died in 1790.
1.5 decades. :')
to all, an outline of the book:
David G. McCullough: John Adams
Summary by Michael McGoodwin, prepared 2001
http://www.mcgoodwin.net/pages/otherbooks/dm_johnadams.html