At the University of California, Davis, retired dean Robert Crummey ticks off the ways that the University Retirement Community keeps him and roughly 350 other residents in touch with campus life.
They work as campus ushers and docents, and they volunteer in research labs as well as the school's arboretum. Some, including Crummey, perform in the university chorus. Some audit classes. Current UC Davis students intern at the retirement facility, and faculty members give frequent guest lectures there.
"The campus effect is considerable," said Crummey, 74.
Forget the notion of traditional, seniors-only, golf-based retirement communities tucked on the edges of distant suburbs. Some experts think the future of retirement living depends not on segregation but rather on social connection -- as at this community, which has no legal or financial connections with UC Davis.
"For the past 25 years, we've mainly built retirement communities on the golf course or on the top of a mountain somewhere," said Andrew Carle, who directs the senior housing administration program at George Mason University in Fairfax, Va.
"That won't be enough for baby boomers. We invented 12 flavors of Coca Cola. We expect more flavors. There are 78 million of us demanding that. We'll congregate, but we want our own groups."
Some niche communities have been around for decades, including faith-based senior housing, senior nudists in Florida and assisted living for retired RVers in Texas.
Newer possibilities are springing up across the country.
Take the Crescendo at Westhaven, a country music retirement community near Nashville, Tenn., scheduled to open in two years. Or Fountaingrove Lodge, an upscale seniors' development opening this fall in Santa Rosa, Calif., catering to the gay, lesbian, bisexual and transgender demographic.
Almost 60 percent of second-half baby boomers -- those born from 1956 to 1964 -- say they plan to buy a new home when they retire, according to the Baby Boomer Report. But only 16 percent of today's retirees have moved to seniors-only developments.
"What we hear from boomer focus groups is that people don't want to move away from the life of the broader community," said Sheri Peifer, vice president for research at Eskaton, a major Northern California senior-living nonprofit. "They want to live near their neighbors. They want to go to the church they've attended for years."
One promising option, she said, involves planned intergenerational neighborhoods of "livable design-certified homes," built to accommodate the needs of empty nesters but available to young, growing families, too.
Despite its founding almost 25 years ago as a nursing home for Chinese- and Japanese-speaking elders, the Sacramento area's Asian Community Center sites today offer housing, health and social service programs across cultural and ethnic lines.
"The notion of affinity retirement communities can go in many directions," said Donna Yee, ACC's chief executive officer. "Many people are realizing they can be retired for 30 or 40 years. They're taking care of their parents now and visualizing what this might say about their own needs as they get older.
"Sometimes, Plan B is that they want to remain among their peers, the people they grew up with and know."
Informal arrangements -- whether co-housing developments or simply a shared duplex -- can work well until the parties involved require more extensive ongoing care, said George Mason's Carle.
On the other hand, university-based retirement communities are booming, with campus-related continuing-care facilities already dotting the landscape from Stanford and Penn State to the University of Florida and another 50 universities.
Typically, at least 10 percent of residents are emeritus professors and retired campus staff members.
"Baby boomers want active intellectual stimulation in an intergenerational environment, because we don't consider ourselves old," Carle said. "That's the college campus."
He sees another largely untapped option for baby boomers: cruise ships.
"You have a hospital and doctors on board," he said. "... It wouldn't work for skilled nursing, no. But for assisted living? Yeah. And you travel the world."