The actress Lucille Ball once said, "the secret to staying young is to live honestly, eat slowly and lie about your age."

But these days, people have found other ways to hold onto their youth: Having plastic surgery, staying fit and waiting longer for big life events like marriage, parenthood and retirement.

In fact, people seem to be delaying major decisions so much that the concept of age in America has changed.

"We're all living longer and [we're] functional longer," said Steve Buxbaum, 33, a financial analyst who lives in Los Angeles and is single. "There are a lot of forces that are allowing us to extend the age deadlines."

Some say that Gen-Xers act more like early 20-somethings or even teenagers, 40 seems like the new 30 and the age at which someone is considered old has shifted.

"Eighty-three is old. Forty, even 50, is not old at all to me. That seems to be the start of everything," said Jennifer McGeorge, 30, a single actress in New York.

Experts say Gen-Xers are putting off marriage for a variety of reasons, but much of their trepidation comes from watching their parents' generation and the high incidence of divorce.

"Gen-Xers are more cautious and perhaps more thoughtful. They plan it out and think about it more carefully," said Barbara Dafoe Whitehead, co-director of the National Marriage Project at Rutgers University. "Baby Boomers threw caution to the wind. They jumped into things without really thinking about it. Gen-Xers are looking before they leap into marriage anyway."

The delay in starting a family has put age on a different track, leading to later retirement and in many cases, healthier, more active lifestyles.

"The expectation of a long life is what's driving all this," said Jim Fishman, publisher of all the AARP Foundation periodicals, including Modern Maturity and My Generation. "They're thinking differently. They're not thinking, 'I'm slowing down.' They're thinking, 'What's next?'"

Thanks to advances in modern medicine and the knowledge that healthy eating and exercise can lead to longevity, many are living well into their 70s, 80s and 90s. The average life expectancy in the U.S. has jumped from 68 in 1952 to 76 last year, according to the Centers for Disease Control and Prevention.

"If they're 60, they may very well have 20, 30, 40 years ahead of them," Fishman said. "People used to get to 50 and look at the downhill slope of their life and think, 'This is the end.' Nowadays, people get to 50 and they're looking at the next phase. They're anticipating a long and active life ahead of them."

In fact, Fishman said, the second-largest growth age group, demographically, is the 100-plus set.

"Retirement means a completely different thing now," he said. "They're working, they're doing things partly because they want to, partly because they're physically able to and partly because there are so many options available to them."

The increased emphasis on good diet and regular exercise has made it possible for people to do much more than they used to be able to in the later stages of life.

"My parents are very active they can do stuff my grandfather couldn't do when he was 65 because he didn't treat himself as well," said Buxbaum.

And then, of course, there's plastic surgery to help those nearing or surpassing retirement look younger while they stay in the game.

"They want to look good and they're doing things about it plastic surgery is one of them," Fishman said. "It's very popular."

An obsession with eternal youth? Perhaps. But with life expectancy increasing, why not do what we can to stay young for as long as possible?

After all, as World War I-era British Prime Minister Herbert Henry Asquith put it: "Youth would be an ideal state if it came a little later in life."