Social Security can be worth more—a lot more, and not just for you but for your spouse—depending on when and how you claim benefits. It can also cost you both.

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Couples claiming Social Security benefits need to consider several factors, Fidelity says, when deciding when to start the checks coming in: their life expectancy, any age difference, and their overall health.

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Failing to do so could cost them big time—or could cost the surviving spouse years later—while a little planning and willingness to postpone claiming benefits as soon as eligible could pay off with bigger checks for many years.

While many people are eager to claim benefits as soon as they’re eligible at age 62, that means they’re going to get a reduced benefit. And they’ll get that reduced benefit for the rest of their lives.

But if they wait till they’re closer to age 70, those checks will be up to 8 percent larger for every year they don’t claim; that means a much bigger check when they finally do apply for benefits.

But of course that won’t do much good if one or the other of you has health issues or comes from a family with shorter lifespans—better to have the money now and enjoy retirement.

For instance, did Great-Aunt Martha live to be 98, or did Uncle George not even make it to 40? Do either or both of you have health conditions that could shorten your lifespan?

Postponing claiming benefits if you’re not likely to live long enough to enjoy them doesn’t make much sense, and the spouse with a likelihood of a shorter lifespan might be better off claiming as soon as eligible.

One or the other of you would have to live into your late 80s before you received as much money as you would have had if you had claimed benefits at age 62—so if that kind of longevity’s not likely, claiming as soon as you’re eligible could be the best option.

Then there’s the issue of a big pay difference between spouses.

The higher-earning spouse might want to postpone claiming as long as possible to grow the benefit for the lower-earning spouse—particularly if there’s a substantial age difference between them.

If the high earner is much older, the lower-earning spouse will be dependent on the survivor check for a long time, so it makes sense to try to increase its value.

The strategy here is for the lower-earning spouse to claim on his or her own work record, and switch to the higher-earning spouse’s record later—when the high earner turns 70, for instance, or as a survivor benefit when the high earner dies.

If you’re both close to the same age and have similar life expectancies, you’re both likely better off postponing claiming benefits as long as possible, since that will result in higher benefits for each spouse—for the rest of your lives.

Maximizing benefits this way lessens the likelihood that you’ll run out of money during retirement.