Drawback of Stop-Loss Orders Earnings and the CANSLIM Method

Early Social Security Benefits and Long Life Spans

For individuals who live a very long time, any decisions to start benefits early at permanently reduced levels will reduce the longevity protection of lifetime benefits and the inflation protection of the COLA. Therefore, individuals who are in good health and have "longevity genes" in their families should carefully consider the long-term cost of starting benefits early. Keep in mind that the current COLA is not guaranteed and could be changed by Congress in the future.
Source: http://www.investopedia.com/articles/retirement/08/6-retirement-myths.asp