When it comes to life expectancy in America, there's good news and bad news. The good news: Americans are living longer and enjoying more years in retirement. The bad news: we can't pay for it.

That's because Americans are collecting Social Security benefits longer than the system was designed to provide. 

When President Franklin D. Roosevelt signed Social Security into law in 1935, it was a lifeline to poor seniors and an easy promise to keep – the retirement age was 65 while life expectancy was 63, noted Rep. Paul Ryan, R-Wis., a member of President Obama's fiscal commission.

"The numbers added up pretty well back then," he said with a chuckle. "It was never designed to be a program that would last 25 or 30 years and so that's one of the reasons why there is so much fiscal pressure on it."

Andrew Biggs, a former Social Security official, said these days a "typical person could spend almost a third of their adult life in retirement supported by Social Security. That's a real burden on the system -- that's a real burden on the taxpayer."

He pointed to the 1950s as an example.

"The typical person claimed Social Security around age 68 and they could live to around age 76," Biggs said. "So that's around eight years of benefits they would collect. Today, the typical person claims Social Security at 62 but lives into their early or mid-80s."

In fact, since Social Security first started paying benefits in 1940, the average life expectancy for men -- once they reach age 65 -- has increased by more than five years to age 83, while women also live five years longer in retirement to age 85.

But an even bigger problem is on the horizon – the retirement of the baby boomers.

According to the Congressional Budget Office, the number of people 65 or older will increase by 90 percent in the next 25 years -- up to 92 million instead of the 53 million now getting checks.

And the number of people paying taxes for all those retirees will grow just 12 percent, so the burden on them will increase.

"The real people who have a stake in this are not the elderly, it's the kids," said Doug Holtz-Eakin, a former director of the Congressional Budget Office. "By fixing this problem, they can look forward to having some Social Security benefits, and they can look forward to having an economy that has not been run to the ground by an enormous deficit."

Jim Angle currently serves as chief national correspondent for Fox News Channel (FNC). He joined FNC in 1996 as a senior White House correspondent.