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.

Those who are living through it spend their time in the traditional American way: pursuing happiness. And so it is that senior citizens 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 are 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, Robinsone 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.

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

A generation ago, romance among the elderly was 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. 

Today, the elderly find remarriage fraught with headaches: It can threaten pensions. It can alarm children worried about inheritance. It comes with love-testing anxiety about liability for a new spouse's health costs. So remarriage rates among seniors are flat.

But, according to Susan Brown, a demographer at Bowling Green State University in Ohio, cohabiting among older people increased 50% 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.

The family's acceptance is key to romances that flourish, said Steve Shields, head of Meadowlark Hills, an adult living center in Manhattan, Kan.

"The need for approval and support from their children is really large," he said.

 "No matter how deeply they love in late life, the importance of the love of their kids never diminishes."