U.S. stock market returns over the past decade or so have been nothing short of spectacular, but far less so for those who chose to retire in 2008, when a 30% decline in the market inflicted irreversible damage.

In the financial-planning world, this reality is called the “sequence of returns risk.” It means that when in the stock-market cycle you choose to start withdrawing from retirement accounts will having a huge impact on how long your investments will last, according to Mitchell Goldberg, president of ClientFirst Strategy, a Melville, NY-based advisory firm.

With the S&P 500 SPX, +0.91%  having gone nearly 10 years without negative annual returns, it’s high time for those who are about to retire to reconsider their stock exposure.

Goldberg, using some calculations by Jason L. Smith, a financial planner and author of “The Bucket Plan,” illustrated how severely negative returns at the beginning or at the very end of a 10-year horizon impact investors.