And that is why financial advisers recommend planning for a long life. Here are some strategies to consider before signing up.

SINGLES Figuring out when to collect is easier when you do not have to worry about how your actions will affect a spouse. It usually pays to wait until your full retirement age if you can support yourself until then. (This obviously does not apply to people who are already in poor health and probably won’t live past 78, give or take a couple of years. People who are still working should also defer.)

Though many experts will tell you to delay as long as you can, waiting from 66 until 70 may not be optimal for some singles. “The reason is that they will have consumed too much of their savings in those extra four years to be able to offset the savings loss with higher Social Security payments within their lifetime,” said Mr. Hebeler, who has also written three books on retirement. “It’s surprising, but that’s what the analysis shows.”

Consider a single person with $200,000 in savings returning 5 percent a year. Instead of taking Social Security at age 62, she withdraws $19,000 annually until she turns 66. Her savings will last until age 94, but she will still have $21,000 a year in Social Security benefits. If she claimed at 62, her savings would run out at age 87 and she would be left with only $16,000 a year in Social Security.

For people with significant savings who expect to live well into their 80s, it may make sense to wait until 70, Mr. Hebeler added.

If you have already started receiving benefits, but wish you had waited, you are allowed to give it all back and start over. But this gets complicated. You will probably have to pay back more than what you actually received each month, since Medicare premiums and income taxes may have been deducted. Married people can do this, too, but some advisers caution against it.

MARRIED COUPLES Planning is more complex for married couples because there are age differences, varying retirement dates and earnings and other factors to consider. In many cases, the higher-earning spouse should delay his or her benefits until age 70, while the lower earner begins to collect at age 62. This ensures that the surviving spouse will end up with the maximum amount of benefits for the rest of his or her life. Even if the higher earner died before age 70, the survivor’s benefits would be bumped up to what the deceased spouse would have gotten, said Lesley J. Brey, a fee-only financial planner in Honolulu.