Is 100 the new 78? A growing number of voices are insisting that you need to be planning a life that will last well past 90. Possibly past 100. And definitely long past 78 which, at birth, is your longevity in the U.S.

Living longer impacts just about everything from how much savings you need to how long you work. Suddenly, living longer than the retirement savings last looks like a very real worry. "Longevity is a big factor in financial planning for retirement," said Ted Goldman, the senior pension fellow of the American Academy of Actuaries and an expert on longevity risk.

Ohio attorney and retirement planner Kevin Fields insisted that worrying about going broke in old age is not irrational. "When you couple increased longevity with the substantial decrease in traditional pension plans being offered by employers, the likelihood that individuals will outlive their retirement savings has increased significantly," he said.

As for how long we are likely to live, Dr. Tom Perls, who has run the New England Centenarian Study at Boston University Medical Center for 25 years, said that in just that time span "centenarians" - people 100 and older - "have doubled. It is 1 per 5,000 people. Before it was 1 per 10,000."

Properly concerned now? "It's a wake-up call to realize you may live to be older than 90," said Perls. He added: "People's perception of what 65 is has dramatically changed."

That is fact. Before, 65 was a marker signaling the approach of end of life. Of course, many had already died before then. But nowadays cheap, effective medicines are helping control cardiovascular diseases, cancer detection and treatment have gotten better, and many of us have eliminated the bad behaviors - such as smoking, eating too much, and not exercising - that hasten earlier deaths. The upshot is suddenly lives are longer.

The U.S. Census Bureau corroborated this. "The nation's 90-and-older population nearly tripled over the past three decades." By 2050, the Census Bureau sees a further doubling of the numbers of people older than 90.

Is there no limit to how long we may live? Perls said some science fiction writers and futurists talk of 1,000-year lives. "That's very debatable," said Perls who indicated that his research presently indicates that living beyond 105 is the challenge. "Those are people who are delaying diseases. It is very rare."

Perls, by the way, offers a free longevity calculator. Answer a handful of questions and you'll get the forecast for your life expectancy. Don't be surprised if it comes back with a lot more years than you had anticipated.

How well have you planned? "Many people get concerned about this in their fifties," said Dr. Jennifer Stagg, author of Unzip Your Genes: 5 Choices to Reveal a Radically Radiant You.

She added: "Your genes are not your destiny. What you eat makes a big difference in your longevity and health."

Probably, for many of us, the easy part is eating better and exercising - at least we know what to do (even if consistently doing it is a different matter for many).

But the one area that very much demands us to take charge is personal finances. "Retirees need to define what their priorities are in different stages of retirement and make choices to improve their chances of living the lives they want," added Tom West, managing director of advisory firm SEIA. He added: "I recommend finding out how much living a life according to their priorities will cost first, and then developing appropriate spending, investing, insuring plans from there."

Factor in living into one's 90s, and this may warrant a rethink of priorities. Maybe you can take early retirement at 62 but is that wise if the math says you likely will live to be 90? Does it make more sense to delay retirement until 70? Or maybe even later, health permitting?

Some retirees also now are spending more frugally in their 70s, said multiple advisors, as awareness grows that today's money may need to stretch for several decades. Decisions like these now have to get made.

Talk with financial advisors, and it's become clear that running out of money is emerging as a new, powerful fear of retirees - but the savvy ones now are working through, often with the help of advisers, the financial scenarios and what their best choices are in a world where centenarians are a fast growing population cohort.

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