More Americans are now working past 75 than ever. 

It's a shift that comes as the oldest baby boomers near their 80s, and better health care enables many older adults to extend their working lives. 

This group might be a fraction of the workforce, but it's the fastest-growing slice. 

In 2002, about 5% of people over age 75 were working in the U.S. — by 2022, that share had jumped to 8%, according to the Bureau of Labor Statistics. By 2032, the Labor Department expects that 1 in 10 people over 75 will continue to work, even as the share of younger workers remains flat or decreases slightly over the same period. 

Many Americans are working into their 70s and 80s — or longer — because of longer life spans, changing attitudes about retirement and insufficient savings. Others simply say they enjoy what they do, and never contemplated giving it up.

CNBC Make It recently asked three people who have continued to work into their 90s to share their best advice for building a long, happy career. Here's what they said: 

Turn your hobby into a career

Jayne Burns, who turned 101 in July, has had the same part-time job as a fabric cutter at Joann Fabric and Crafts store in Mason, Ohio for 26 years. 

The centenarian tried retiring several times from her career as a bookkeeper throughout her 70s and 80s, then would "unretire" just a few months later, taking part-time jobs at veterinarian offices and accounting firms. 

"I like the routine, I like to keep moving," she says. 

Burns, who has sewn for most of her life, started as a customer at Joann. She quickly built a rapport with the store's employees and enjoyed recommending different fabrics to other shoppers. 

In 1997, just a few months after her husband Dick died, a fabric cutter position opened at the store. Her daughter, Donna Burns, was working at the store part-time and recommended her for the role, thinking it might be a welcome distraction from the grief.

Donna was right. 

Burns feels that her job is less of a chore and more of an opportunity to learn more about a hobby she loves and meet "interesting, kind" people.

"I enjoy what I do, so I want to keep doing it," she says. "I'll work for as long as I can or as long as they'll have me."

Plus, she adds, "Staying busy keeps you from focusing on your aches and pains. It makes it easier to keep going."

Don't be afraid to ask for what you want at work

Melba Mebane, 91, retired from her job as a sales associate at the Dillard's department store in Tyler, Texas in July, leaving behind a career that spanned more than seven decades.

Mebane began working as an "elevator girl" at the Mayer & Schmidt department store in 1949 when she was just 17 years old, through a work-study program at Tyler High School. The store was acquired by Dillard's in 1956. 

She moved to the men's clothing department then later the cosmetics counter, where she stayed until she retired.

To be happier at work, "it's important to invest in your relationships," Mebane says, so you can tailor your job to your interests and craft a more fulfilling career.

Mebane leveraged her close relationship with the chain's founder, William T. Dillard, to tailor her job to her changing needs and desires throughout her career.

When she turned 65, she considered retirement, but Mr. Dillard convinced her to stick around — only after Mebane got him to adjust her schedule, so she didn't have to work after 5 p.m. or on Sundays.

A few years ago, she also convinced her manager to replace the hard linoleum on the floors behind the cosmetics counter with soft carpeting, as standing most of the day was getting less comfortable. 

During her tenure at Dillard's, Mebane had several opportunities to become a manager, but she always turned the offers down. 

"Nobody likes management, because they have to make the tough decisions," she says. "I liked my friends at work, and I wanted to keep them, so I just focused on being the best salesperson I could be." 

Those friendships, Mebane says, made working at Dillard's "the best job I ever had."

Work with people you love

Bob Rohloff has been a barber for 75 years — and at 91 years old, he doesn't plan on retiring anytime soon.

The Wisconsin native started cutting hair in 1948, training under his dad, Erv, who was a barber. Back then, a haircut cost 75 cents.

"Believe it or not, we made a lot of money every week and we got excellent tips," says Rohloff. "Plus, my dad was my best friend, so working with him was really fun."

He credits much of his success to his dad, who introduced him to other barbers who were hiring, and always gave him honest advice about "what it really takes to be a barber, and how I could improve my work," he says.

Up to this point, Rohloff's career has taught him the importance of working with people you love, he says, whether it's your boss, co-workers or the customers you interact with. 

Rohloff tried to retire 15 years ago, but "unretired" just a few months later because he missed the camaraderie and conversation of the barbershop.

"Retirement isn't that easy," he says. "You need to stay active in something, whether it's a hobby or a job, and I happened to enjoy my job very much … it's fun coming into the shop, I like to do it and I feel good, so why stop?" 

In June, Rohloff and another local barber, Mark Karweick, opened Bob's Old Fashioned Barbershop in Hortonville, Wisconsin, a 20-minute drive from his hometown, Black Creek.

The best part about running his own shop again, Rohloff says, is meeting new people. 

"They're not just customers, they become fast friends," he says. "We have customers who bring us maple syrup, people that will bring us vegetables from their farms or even homemade sauerkraut … you don't get that working in a big city." 

As for what Erv would think of his son continuing to cut hair at 91, "He wouldn't believe it," says Rohloff. "But he worked until he was 85, so I think he'd be proud."

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