For David Lincer, 67, the question of longevity once felt straightforward. He initially imagined living to 93 — close to the national ideal of 91, according to a recent survey. Now, numbers matter less to him than his physical health.

“I’m not interested in living life out in a bed just to say I made it to 100,” Lincer said.

Even as the number of centenarians is expected to quadruple over the next 30 years, the majority of adults agree with Lincer. A recent Pew Research Center survey found 29% of Americans hope to live to 100. Many say their hesitation comes from the potential of declining health, limited finances or social isolation that could accompany the additional decades.

Lincer runs an elevator installation business that requires climbing, lifting and heavy physical work, and is generally healthy. He jokes that he can still outrun his younger employees up a hill. But recent lab tests showing he is “on the borderline” for diabetes have pushed him to focus more intentionally on his health.

He cut out sugar and continued his weekly yoga practice. Several years ago, after a physician warned him about his cholesterol levels, he made dietary adjustments and improved his numbers: a reminder, he said, of the importance of being proactive about health as one ages. His healthy habits have also been shaped by watching his mother’s decline; she developed Parkinson’s and later suffered a stroke during a medical procedure.

“I want to stick around with a good life,” he said. “If I can’t enjoy it, get me out of here.”

Researchers say these concerns mirror those expressed by many adults. The Stanford Center on Longevity has started the New Map of Life, a multi-year initiative aimed at rethinking what longer lifespans might look like. In a survey the center conducted with Time magazine, respondents said their top hopes for if they reach 100 were avoiding dementia and staying financially sound.

“We found people still associate growing old and being very old with declining physical and cognitive health,” said Yochai Shavit, a researcher at the center. “We are in desperate need of a positive vision of what 100-year lives can look like.”

The cash crunch is real. On average, assisted living can cost $6,694 a month, about twice the average monthly rent in the Bay Area. The Pew study found a direct link between financial security and health outcomes. Only 26% of low-income seniors reported being in very good or excellent health, compared to 49% of those with the highest incomes. This changes the picture of living to 100: More than four in 10 adults are not confident they have enough cash to cover their retirement years.

Beyond money, there are other things seniors can do to make the prospect of living to 100 more appealing: Avoiding social isolation is part of staying sharp. Tee Lynn, 75, has leaned into community as she’s aged. A former school counselor, Lynn keeps a small circle of friends and volunteers at the Downtown Oakland Senior Center throughout the week. But, even as a self-proclaimed “lover of life,” she imagines living to about 85 or 90, and is unsure about the value of reaching 100.

Even those with a solid community still worry about the physical frailty that can come with age. Marina Miranda, 69, also has found friends at the Downtown Oakland Senior Center, where she spends most weekday mornings knitting and working on puzzles.

“I don’t like being stuck in the house. All you have is TV. And it gets hard if you don’t have a social life when you’re older,” she said.“I do have one fear as I age: if I become disabled, who will take care of me? I just live day by day, you can’t think about the future because you don’t know what’s gonna happen, and you can’t control what’s gonna happen in life.”

Her attitude toward control reflects a larger truth about aging. According to the Pew study, only three in 10 adults say they feel they have a fair amount of control over how they age, including their mental and physical health. Miranda maintains what control she can: small routines, polished nails, daily conversation at the center.

Like Miranda, Chuck Sieloff, has no target age. At 83, he is a longtime member of Avenidas Village, an aging-in-place program in Palo Alto, where he leads a monthly discussion group called the Healthy Aging Group. It is work that gives him insight into what he wants for his future.

“I’m a huge believer in ‘health span’ over lifespan,” he said. “It’s not about how long you live, but about how long you remain healthy.”