It's the question that can keep you up at night after age 60: When should you start collecting your Social Security benefit? Some argue for delaying your federal retirement benefit until qualifying for the maximum amount at age 70. But there's one major reason why that's a bad idea.

Waiting until you're 70 to claim Social Security raises your monthly benefit, but it can lower your cumulative lifetime benefit. This happens if your lifespan ends up being shorter than the average. To put it bluntly, if you die before turning 80, you'll probably get less from Social Security by waiting to claim.

The numbers on claiming late

As you may know, you can start collecting Social Security anytime after age 62. But at that age, you qualify for your lowest possible benefit, and your monthly only increases over time (up to age 70).

A major determinant of your benefits in that window of time is your full retirement age (FRA). FRA is the age you qualify for your full benefit, without reductions or credits. If your FRA is 67, claiming at age 62 reduces your benefit 30%, while claiming at 70 earns you a 24% raise.

Two people smile at each other while walking bicycles outside.

Image source: Getty Images.

Those who choose to wait are rewarded with higher income, but they have to forgo some cash up front too. Say your benefit at your FRA of 67 is $1,500 per month. Waiting until age 70 means you'll skip three full years of income -- which adds up to $54,000.

Meanwhile, the extra 24% you get for delaying your benefits until 70 adds up to an extra $360 per month, or $4,320 annually.

Putting it all together, it would take about 12 and a half years for your extra $360 monthly to make up for the $54,000 your give up by delaying your benefits. Breaking even wouldn't happen until you're 82. If you don't live that long, you would have earned a bigger lifetime benefit by claiming earlier. This is why taking your life expectancy into account is key to maximizing your Social Security income.

Predicting lifespan without a crystal ball

At this point, you're probably wondering how you're supposed to predict your own lifespan. This is the tricky part -- you can't know for sure whether you'll celebrate your 80th, 82nd, or 95th birthday.

Fortunately, there are free resources that can help you determine your life expectancy. Known as life expectancy calculators, they collect information on your health, lifestyle, and family medical history. They use your responses along with actuarial lifespan tables to predict how long you'll live.

It's a morbid exercise, for sure, but these estimates could help you make a financially savvy decision when it comes to your Social Security benefits.

This is also a conversation you should have with your physician. They can identify your biggest risk factors and behaviors. There's always time to shift into a healthier lifestyle with the goal of extending your longevity.

Live long and prosper

Hopefully your lifespan estimates predict many birthday celebrations ahead. In that case, you might base the timing of your Social Security on other factors too -- such as how long you want to work or how much income you'd like to collect in retirement. From a lifetime benefit perspective, delaying your claim until 70 generally works in your favor only if you live into your 80s.

Perhaps the larger lesson here is this: You can get more from your Social Security -- and retirement in general -- by staying healthy and taking care of yourself.