Who was the longest-serving member of the US federal cabinet, and who has held the most cabinet posts?

Answer 1

Elliot Richardson served in four Cabinet-level positions:
Secretary of Health, Education, and Welfare from 1970-3
Secretary of Defense from January to May of 1973,
Attorney General from May 24 to October 1973,
Secretary of Commerce from 1976 to 1977.

As for the longest serving,I think it's Alan Greenspan the
former Chairman of the Federal Reserve. But..he was and
wasn't a member of the "cabinet". He was Level 1 in the
Executive Schedule. Which means nothing to you,I'm sure,
but it's a "cabinet level officer". ( You are appointed by the
President and report to Congress 2x a year,etc.) I give
Old "Irrational Exuberance "the nod for longest serving.

Answer 2

Lance Armstrong---7 titles in a row!