As the baby boom generation goes through another rite of passage at 65, America must gear itself for economic, social and cultural changes that this would bring.
As the first of the 76 million US boomers reach the magic age in 2011, they will likely transform the notions of retirement and old age instead of following in the footsteps of their parents, say experts.
The demographic trend means a shock to the economy, government finances, a strain for the health care system, and even a potential shift in America's role as a global superpower.
But analysts say this won't be your grandfather's retirement.
"Even though 65 is the conventional retirement age we've become accustomed to, this generation doesn't look at retirement as the kind of cliff-ending of a career that previous generations had to experience," says John Challenger, chief executive of the consultancy Challenger Gray & Christmas.
"Today for many reasons both chosen and not chosen people are working for a much longer period at this stage of their lives. There are many studies showing that continuing to find meaningful work into your 60s and 70s is an important part of health and longevity and life balance."
A report by insurance firm MetLife confirms this view. It shows fewer than half of boomers expect to be retired between the ages of 65 and 69, whereas in the past three-fourths expected to be retired within a few years of hitting 65.
Report author and demographer Peter Francese says the first of the generation, the so-called "leading edge" boomers have a tradition of being "trailblazers."
"This group was among the first for whom college education was commonplace. They were also among the first to have a sense that their lives would be better than those of their parents," he said.
"While their retirement years will be met by financial challenges, they may end up having more social and personal fulfillment than that of their parents through their continued presence in the workplace."
Similar demographic trends are occurring in most major industrialized nations, but the US population will not age to the degree of most of Europe or Japan, notes Richard Jackson, director of the Global Aging Initiative at the Center for Strategic and International Studies.
Jackson wrote recently that for the US, "relative demographic strength will tend to cement its geopolitical power," but that "the mounting demographic weakness of its traditional allies could undermine their ability to shoulder part of the global security burden."
Even so, Jackson told AFP that the US will see a "fiscal shock" and "labor market shock" as older Americans stop working and collect social benefits.
The trends point to "a potential for a growing conflict or competition between the young and old over scarce public resources," said Jackson.
This means a likely renegotiation of the "social contract," says Jackson: "We should have been doing this 20 years ago. Boomers are turning 65 but there's not much time to prepare and adjust."
One bright spot is the increasing vitality and health of the population, meaning they can work and contribute more in ways they had not in the past.
"Old people today are younger than old people of the past: Today?s 75-year-old man is the same 'age' as a 68-year-old man in 1970. Thus, 75 is the new 68," says a report by the Stanford University Center on Longevity.
Challenger said new technology and flexible workplaces will make it easier for older workers to stay active.
"There are frictions over technology and its adaptation, but each year more of the older generation gets comfortable with technology, so technology also facilitates the ability of older workers to continue their working lives," he said.
"It also allows people to telecommute. We no longer work from 9:00 am to 5:00 pm in a particular space."
Sandra Timmermann, director of the MetLife Mature Market Institute, said older workers are capable of handling the mostly white-collar jobs that are open to them.
"This group of highly educated individuals is also apt to find a welcoming employment market where their experience is desirable," she said.
Jackson says some research suggests these "younger" elderly want to avoid being ghettoized in retirement homes and communities, and may opt instead to stay in the homes or move in with children in multigenerational families.
"The whole notion of retirement as a life cycle phase is basically a post-World War II concept," he said. "Before that, it was something you did to an old machine. We may be moving back to a society where older people are more engaged."