As I tell my clients, retirement is not a homogeneous phase of life but typically consists of three phases. Being a participant in the "go-go" phase I can assure you that many newly retired persons spend more in this phase than they did while working. Sixty days on a motorcycle trip from Utah to Cape Breton Island in Nova Scotia, Canada cost far more than two months at home, even with staying with relatives and camping for part of the time.
Michael K. Stein, CFP, is credited with the first time I read about the three phases of retirement in his book "The Prosperous Retirement: Guide to the New Reality" 1998, EMSTCO Press.
Read more about investing for and anticipating the differing expenses of the three retirement phases in an article in US News and World Report by Jeff Brown at: http://money.usnews.com/investing/articles/2016-08-08/how-to-invest-in-retirement