Baby boomers have been the golden children of American culture for 60 years, and society has reshaped itself to accommodate their wants and needs. And by Jan. 1, 2011, one will turn 65 every nine seconds, which may force marketers to rethink the core youth-oriented demographics that they’ve relied on for decades.

Though real maturity looms, baby boomers, who are now between the ages of 46 and 64, still protect their relative “cool” with a vengeance. “They want to remain vital,” says Matt Thornhill, founder and president of the specialty research firm Boomer Project. “Sixty is no longer old. Remember Granny on ‘The Beverly Hillbillies’? She was 62, but no one thinks of Goldie Hawn as old, and she’s a grandmother.”

Marketers will have to adjust to the evolving boomer state of mind, says Thornhill, if they want to retain boomers as customers. At this stage of their lives, they’re looking for products that are “easy to use and designs that delight them” he says, like the curved shower rod, which bows out to make more room for an overweight person or to make a standard-size person feel less crowded.

Baby boomers are “more useful and youthful than the previous generation” says Iris Schencke, a California-based Finnish artist and co-author of the book “Ergonomic Living: How to Create a User-Friendly Home & Office.” They produced teen culture, revolutionized sex and shamelessly pursued wealth and individualism. “But they won’t admit to being creaky now,” she said, which affects how they interact with personal spaces. “But boomers are more willing to spend to make themselves happy and comfortable — and are likely to change aging.”

Baby boomers aren’t trying to stop the clock, however. “They feel younger than they are, but they’re not trying to be young,” says Thornhill. “They’re not making 60 the new 40. They’re making 60 the new 60.”

At home, baby boomers look to add furnishings that address their burgeoning aches and pains while satisfying their seemingly incompatible forever-young mind-set. They don’t want to hear about being old. They just want to know that a product works for them.

Schencke says that successful furniture makers will adjust to the human being — in this case, baby boomers — which is what ergonomics is all about. She believes chairs will undergo the most radical change to support a rash of stiff backs and necks, and she thinks “really good office chairs by Herman Miller or Knoll would be great at home.”

One in four Americans is a baby boomer, and there are about 78 million of them, which, by most estimates, is still the largest generation in U.S. history. Some experts say Gen Yers, also called echo boomers, are anywhere from 65 million to 80 million strong, but since they were born between 1980 and 1995, they are still too poor to be a market force and they’re too young to creak.

Meanwhile, baby boomers, who outspend other generations and tend to be married and still earning money, will have to re-create their main living areas if they’re going to negotiate what Thornhill calls “the middle of middle age” in their characteristically breezy and disobedient way. According to Furniture Today, a trade publication on the Web, 54 percent of them are redecorating this year. Whether they’re remodeling an existing home or furnishing a new smaller or second home, they are ready to buy whole rooms of furniture.

Bill Ness, president and founder of 55places.com, a Chicago Web site that specializes in new communities for adults 55 and older, says baby boomer furniture buyers often fall into two categories: those looking for a new home that fits their existing furnishings — which include sentimental pieces and heirlooms — and those starting anew by shedding the old house and furniture for brand-new everything. In either case, “they don’t want to buy anything that screams older adult but they want the things in it that they may one day need,” like lever door handles instead of knobs, wide hallways to prevent bumps and bruises, sleeper sofas for occasional overnight guests and no stairs to climb at the front door.

Bernice Rosenthal, design project manager for national furniture retailer Ethan Allen, says baby boomers want function and elegance that will last because “it’s their first time buying really beautiful furniture in a fully designed space.”

Lauren Vance, a junior design consultant in Ethan Allen’s New York City showroom, says this demographic shows a preference for transitional furnishings — clean and simple yet sophisticated, styles in muted color palettes — that mix well with contemporary elements and pieces they’ve saved from their old, often traditional, spaces.

“They all have treasures,” like special vases or dressers, says Rosenthal, “that they want to restore and make fit into the new design, but they now require a sleeper sofa for the grandkids, and they will get a recliner.” Her voice deepens when she mentions the recliner, to emphasize the point, as recliners used to be one of the items a self-respecting boomer would resist.

Larry Smith, president of Barcalounger, the Virginia-based 70-year-old furniture maker known for its high-end recliners, says the company offers physical-assistance, power-activated products that appeal to baby boomers. “So no levers to pull,” he says.

And the days of knickknacks and trinkets are over, says Rosenthal. “Boomers want to look at pretty things, but they’re not into collections. They like art, but not collections.” Rosenthal says it’s too much clutter that attracts too much dust. Schencke says “decluttering” is another hallmark of a boomer-appropriate space.

Chicagoan Debbie Dempsey-Amsden says she and her husband had planned to sell their suburban home to move downtown but decided to remodel instead when her mother took ill. “We’re actually trying to get rid of stuff.”

Most of all, baby boomers care about durability and timeless appeal, because they don’t want to spend time cleaning and repairing. Paradoxically, what they buy now has to last, though they don’t want to acknowledge that this might be the last time they decorate a home. Rosenthal says, “Let them tell it, nobody’s ever going to die.”

Another baby boomer couple in Southern California, clients of interior decorator Brendan McBreen — former creative director for Rachel Ashwell Shabby Chic Couture — specifically requested “quality” from the designer, also expressing concern for the environment. For the home that they’re preparing for retirement, he installed reclaimed hardwood flooring throughout, soapstone counters and a subway-tiled backsplash in the kitchen, and “bench-built, hardwood-framed, eight-way hand-tied, down-wrapped” sofas upholstered in strong woven fabrics like linen. “All functional and aesthetic and environmental,” he says, “and it all ages well and has a timeless look.”

Most of all, baby boomers will need good lighting in uncluttered spaces, with furniture that supports mobility, says Schencke, a baby boomer herself. She says ergonomics will eventually become the chief consideration to prop up aging bodies. “Knees get creaky. Backs get creaky. The eyesight is not as good.” And it gets harder to get in and out of “fashionable” sofas and chairs that are low, deep and wide.

But she’s convinced that her generational compatriots will still do things their way, including aging. “A lot of people adjust themselves to the things around them,” says Schencke. Not baby boomers.