John Piper‘s Don’t Waste Your Life (Wheaton: Crossway, 2003) includes this convicting paragraph (pp. 45–46):

An American Tragedy: How Not to Finish Your One Life

I will tell you what a tragedy is. I will show you how to waste your life. Consider a story from the February 1998 edition of Reader’s Digest, which tells about a couple who “took early retirement from their jobs in the Northeast five years ago when he was 59 and she was 51. Now they live in Punta Gorda, Florida, where they cruise on their 30 foot trawler, play softball and collect shells.” At first, when I read it I thought it might be a joke. A spoof on the American Dream. But it wasn’t. Tragically, this was the dream: Come to the end of your life—your one and only precious, God-given life—and let the last great work of your life, before you give an account to your Creator, be this: playing softball and collecting shells. Picture them before Christ at the great day of judgment: “Look, Lord. See my shells.” That is a tragedy. And people today are spending billions of dollars to persuade you to embrace that tragic dream. Over against that, I put my protest: Don’t buy it. Don’t waste your life.

(Don’t Waste Your Life and the study guide are available for free as PDFs.)

I just became aware of a related 32-page booklet:

John Piper. Rethinking Retirement: Finishing Life for the Glory of Christ. Wheaton: Crossway, 2009.

Rethinking Retirement is already available for free as a PDF. (I must have missed it when Desiring God highlighted this on October 7, 2008.)