A 2005 study by Merrill Lynch found that 77% of men and women ages 40 to 58 plan to work in retirement.  Some of these people will become consultants in the industry in which they worked all their lives, while others will embark on a completely new career.  A retirement job can boost your nest egg significantly.  Assuming you retire at age 65, work two days a week earning 40% of what you earned before retiring, you can increase your savings by 30% over a five-year period (assumes 6% annual return and an annual inflation rate of 3%).  Working during retirement also helps to maintain a social network that has been found to be key in maintaining a meaningful life.

"Retirement at sixty-five is ridiculous. When I was sixty-five I still had pimples." ~ George Burns