Retirement is getting old.

Though the average retirement age is 63, some stay at their jobs for decades longer because they love what they do. Take Supreme Court Justice Ruth Bader Ginsburg, who hopes to stay on the bench until age 90. “I’m now 85,” Ginsburg said in New York on Sunday, after watching a play about the late Justice Antonin Scalia, as CNN reported. “My senior colleague, Justice John Paul Stevens, he stepped down when he was 90, so I think I have about at least five more years.”

Ginsburg, a fierce advocate for gender equality and the second woman to be appointed to the U.S. Supreme Court in 1993, joins several other influential woman who refuse to retire anytime soon.

Actress Betty White, who celebrated her 96th birthday this year, has said she’ll keep acting until people stop hiring her. “She told me, ‘I’m going to be in the saddle forever,” Steven J. Boettcher, who co-directed the new PBS documentary “Betty White: First Lady of Television,” told Closer Weekly. And White told Parade magazine recently that even after almost 80 years in showbiz, “I just love to work, so I’ll keep working until they stop asking.”

Jane Fonda, 80, who most recently starred in “Book Club” with Diane Keaton, 72, and Mary Steenburgen, 65, just confirmed last week that she is producing and acting in a sequel to the 1980 hit “9 to 5” with Dolly Parton and Lily Tomlin about 40 years after its debut.

See also: A “9 to 5” sequel is coming because little has changed for working women

And model Maye Musk, mother of billionaire business magnate Elon Musk, is defying ageism at age 70, voguing alongside Karlie Kloss in a recent Swarovski campaign. “My mother worked as an artist until she was 96. You need to know that you can continue to work at any age,” she wrote in an essay for Moneyish in March.

The average U.S. retirement age is 63, according to a 2016 report, and has increased by one year since 2014 — and by six full years since 1991, when the average retirement age was 57.

Some Americans report working well past 63; sometimes because, like the women above, they love what they do and don’t want to stop. But the sad reality is that many keep up the daily grind long into their golden years because they can’t afford not to: They still need to provide for their families, don’t have enough money to retire on, or fear losing government benefits like Social Security and Medicare, experts say.

Forty-two percent of Americans have less than $10,000 saved, and expect to retire completely broke, according to a recent GoBankingRates report. Women have it even worse: 64% say they would like to live to 100, but few feel financially prepared, with 44% of women worried that they will run out of money by age 80, according to a recent study on women and financial wellness from Merrill Lynch. And while the typical retirement costs $738,000, only 9% of American women have $300,000 or more saved.

SEE ALSO: This may be one big reason you haven’t saved enough for retirement

Plus, bigger nest eggs come to those who wait. Age 62 is the earliest you can claim Social Security retirement benefits in the U.S.; but, if you start collecting at that age, the monthly payout will be up to 30% less than what you could get by waiting until you’re 66 or 67, financial expert Suze Orman wrote in the August issue of AARP The Magazine. She also noted that you could get a 75% higher monthly payout by waiting until at least 70.

More money isn’t the only benefit of working later in life. Staying on the job longer also improves mental health, stamina and even how long you live. A study from Cornell University and the University of Melbourne found that men who claim their Social Security at age 62 have a 20% greater risk of mortality. And researchers at Harvard found that retirees are 40% more likely to have had a heart attack or stroke than those who were still working.

“It keeps you engaged; it keeps your brain working,” Susan Weinstock, the AARP vice president for financial resilience programs, told Moneyish. “[When you retire] social isolation is a concern, and going to work every day is going to make that very hard to happen because you’re going to be interacting with people. It’s good to have a purpose in life.”

“It’s not just about the money; people worry that they’re going to become irrelevant,” agreed Lynn Ballou, a certified financial planner at EP Wealth Advisors in Lafayette, Calif. “Secondly, they’re worrying about the limited resources they might have. There’s this fear that the government is taking away social benefits we were promised for years.”

But that’s not stopping some millennials (defined here as ages 18 to 37) from somehow believing 61 is the optimal age to retire, according to Bankrate.com — two years before the average American leaves the workforce and a far reach for many, because they often haven’t been in the workforce long enough to realize how much they need to save, financial experts believe.

SEE ALSO: This is the ideal age to hit every financial milestone, according to millennials

For those looking to retire sooner rather than later — or those who just want to get their retirement savings back on track — it’s important to rethink your consumption and ask yourself, “Do I want this now, or later in life?” when it comes to buying experiences rather than necessities, said Kent Rentschler, a wealth strategist at PNC Wealth Management.

“I have my clients focus on tracking spending so you really know where the money goes day in and day out. That’s where clients eyes’ are really opened, specifically in categories like food, entertainment and travel,” Rentschler said. “When you know where that money goes every day, you can make a plan to cut back some of that consumption.”

Read here for more tips to increasing your retirement savings:
This could be why you’re having trouble saving money

What gig economy workers can do to save for retirement