Here are some other steps retirees can take to lengthen the life of their savings when markets are less than cooperative:

Portfolio Check. Retirees need to ask themselves a couple of key questions. Is my portfolio broadly diversified in low-cost investments, such as index funds? Is my allocation to stocks one that my stomach can handle should the market plummet 50 percent, as it did in 2008 and 2009?

If you answer “no” to these questions, you should reassess (preferably with a pro) how reducing your stock exposure might change your ability to spend what you want in retirement.

Mindful Spending. One of the most widely cited rules for retirement spending might be what’s known as the 4 percent rule. It suggests that retirees who withdrew 4 percent of their initial retirement portfolio balance, and then adjusted that dollar amount for inflation each year thereafter, would have created a paycheck that lasted for 30 years. (The numbers crunched by a financial planner more than two decades ago were based on a portfolio evenly split between stock and bonds.)

But if your portfolio value takes a significant hit, your withdrawal rate may have to increase to support your spending. If that rate starts to approach 5 percent, and certainly 6 percent, there’s a greater chance you’ll outlive your portfolio, Mr. Pfau warned. So adjustments may be in order.

The simplest way to deal with a dip would be to hold your spending steady, rather than increasing it with inflation. That approach can be enough to steady your finances even if your portfolio were to drop by 25 percent from its original value at retirement, according to Judith Ward, a senior financial planner with T. Rowe Price, based on a recent study. She suggested to keep spending steady for two to four years, depending on when the portfolio rebounds.

“Keep in mind, steady spending over a number of years may still result in some kind of spending cuts depending on the inflation environment,” she said. “That may be the easiest and most intuitive approach for many retirees.”