In August 1978, Mills was hired by the Nebraska Association of County Officials as its executive director, succeeding former State Senator
Gerald Stromer. He resigned from the legislature on September 1, 1978. He served as executive director of the association until he retired on June 30, 2000. Mills also served on the board of directors of
Blue Cross Blue Shield of Nebraska, including as chief executive officer and as chairman of the board, ultimately retiring in 2012. ==Death and legacy==