Washington ? Murray Katz, 82, a retired senior federal patent-appeals examiner, has made a transition that lies ahead for millions of Americans.

“When I was growing up, I didn’t see women who were in their 60s and 70s as women,” he said recently. “Now, it’s amazing. The men I know are all looking at 80-year-old women. They’re our friends. We listen to them. We dance with them. We have sex with them when we can. It’s beyond comprehension.”

For many it’s unimaginable. But one of the things new under the sun since Katz was a boy is an 18-year increase in U.S. life expectancy, much of it spent in healthy retired life.

Pursuit of happiness

Those who are living through it spend their time in the traditional American way: pursuing happiness. And so it is that seniors today aren’t just dating more, they’re the fastest-growing users of Internet dating services and the fastest growing group of cohabiters.

To be sure, older men remain in short supply and millions of widows decide that meeting one man’s needs was enough. A few million more are ailing beyond caring. Still, there more couples than ever like Eleanor Robinson and John Kunec.

She’s 85, a Scrabble player, poet and table tennis champ whose social hub is the bustling Holiday Park Senior Center in Wheaton, Md., just north of Washington. He’s 83, fit and friendly, a retired government accountant. Both are widowed.

As surely as she carries his harmonica in her tote bag and they finish each other’s sentences and watch ballgames together, they’re a couple.

“I never had a relationship such as I have now,” confided Robinson, a Roman Catholic from West Philadelphia who married at 19 and was widowed 54 years later.

“It’s like I’m a kid,” she said. “When I’m with him, I’m caring for him, and when I’m not with him, I’m thinking about him.”

Her beau – still a term in their set – had less to say. But Kunec’s a fine harmonica player, and the first tune out of his mouth during the intermission at a recent senior center dance was a stately rendition of the old Ray Charles hit “I Can’t Stop Loving You.”

Nonetheless, the couple maintain separate houses and marriage isn’t in the picture. “The complications wouldn’t be worth it,” Robinson explained. “I’ve limited income that I’ve decided to share with my grandchildren and I wouldn’t want to interfere with his family.”

Longer lives, more money

Multiply this by a million or two, drop the ages by a decade or more, and you have a more accurate picture of what many seniors are up to these days, or would like to be.

Longer healthy life expectancy is part of the explanation. There are also more men around, thanks largely to better drugs and treatments for diseases that more often afflict men, such as heart disease and cancers of the prostate, colon and rectum.

Seniors are also richer, their constant-dollar incomes more than triple what they were in 1960. Sex is hardly out of the question, thanks to Viagra and its cousins, which about 14 percent of senior men use, according to an AARP study.

Finding partners is easier, too, the Internet being a superior resource to barstools or the friends of friends. According to Mark Brooks, a consultant and newsletter writer who tracks the Internet-dating industry, the number of seniors joining online dating services has risen at double-digit rates annually since 2003, the most of any age group.

Changing attitudes

But attitude changes are probably the biggest factor in the expanding social lives of seniors.

A generation ago, romance among the elderly was widely derided, said Pepper Schwartz, a University of Washington sociologist who’s studied dating among older adults.

“Falling in love at an elderly age was seen as somewhere between unwise and dementia,” she said. In the parlance of the day, only “dirty old men” pursued sex. Cohabitation was not just low-class, as the term “shacking up” implied, it was morally “living in sin.”

Today, the elderly find remarriage fraught with headaches: It threatens some pensions. It alarms children worried about inheritances. It comes with love-testing anxiety about liability for a new spouse’s future health costs. So remarriage rates among seniors are flat.

Instead, Schwartz said, “People who wouldn’t have let their daughters into the house if they were cohabiting are now doing the same thing.”

Breaking it to the kids

According to Susan Brown, a demographer at Bowling Green State University in Ohio, cohabiting among older people increased 50 percent from 2000 to 2006, based on census figures.

The total – 1.8 million – counts only couples who live together full time and were willing to admit it to census interviewers. Part-time cohabiting – traveling together, sharing a summer house, spending weekends together – is up at least as sharply, according to seniors and people who work with them.

Does anyone in their age group disapprove?

“Maybe in the red states,” sniffed Eve Jacobs, 87, of Friendship Heights, Md., a labor demographer who still publishes in the field.

Opposition is more likely from children whose widowed parents are newly in love, said Joanne Wilder, a Pittsburgh lawyer and the editor of the Journal of the American Academy of Matrimonial Lawyers.

“Many of them take a pretty dim view of this behavior,” she said, and their parents know it. “Matrimonial lawyers see a lot of people looking for ways to break things to the kids,” Wilder continued. “They’ll say, ‘My daughter will kill me!’ or ‘They really like her, but I don’t think they’d like it if we got married.'”

Consequently, prenuptial agreements are much discussed at poolside in adult communities. “They make it safe for his kids to like you,” said Linda Stevens, 70, of Arlington, Va.