“I don’t think it would work as well if we lived together,” said Mr. Demetre, a 63-year-old retired draftsman who spends several nights a week at her apartment because it’s bigger. The only downside, he says, is the 15-minute drive.

“The assumption is that if you really love each other, you will live together. My question is ‘Says who?’” said Ms. Hyman, 56, a filmmaker who is making a documentary about living apart.

Couples in the second half of life are rewriting the terms of their relationships. Rather than marry or live together, many of them have separate homes and see each other several times a week, or three times a month; they often say they are highly committed to each other but want personal space and independence.

With the rise of “gray divorce,” and a doubling of the divorce rate for those 55 and older, there is a larger pool of single adults who may want a long-term partner, and want to make to it work without entangling finances or relationships with adult kids.

It’s a “new frontier in partnered relationships,” says Susan Brown, a sociologist and co-director of the National Centre for Family and Marriage Research at Bowling Green State University, in Ohio.

Dr. Brown found in a survey of 2,166 adults ages 50 to 65 that nearly one-third of those in an unmarried relationship were in a committed long-term relationship but living apart – an arrangement academics often call “living apart together” and one that Dr. Brown expects to become more prevalent.

Unmarried partnered adults between the ages of 57 to 85 were twice as likely to have separate homes as to live together, Jacquelyn Benson, assistant professor of human development and family science at the University of Missouri, found in a 2017 study. That arrangement appeals to men and women for different reasons, she found in an earlier study. Men want to protect their leisure time; women want to protect their autonomy, she said. But both “step up to the plate” when the other needs care.

These couples “are fulfilling a lot of the function of family for one another,” she said.

Twice a month, David Scribner, 64, drives three hours from his home in St. Johnsbury, Vt., to Montreal to spend a long weekend with his partner, Marilyn Bronstein, 71. She visits him one weekend a month, although she spent weeks with him after he had surgery. The fourth weekend they are on their own.

They don’t talk or text or FaceTime daily. They email when they must, usually keeping the message direct: “Bring the tent” in the subject line. “We mostly communicate with each other when we see each other,” Ms. Bronstein said.

The couple met at a bluegrass music festival in the mid-1990s. Both were divorced. Neither wanted to move because they had careers and, at the time, younger children. Now the kids are grown, but they still don’t want to move. She loves the city. He likes the quiet of the country. They are financially independent of each other and want to keep it that way.

Mr. Scribner says distance and compressed time together enhances their relationship. “I would prefer to be in a state of wishing I was there and being thrilled to be with her,” he said, “rather than living with each other all the time and turning into a gray, monotonous relationship.”

Barbara Leslie and Mike Nieters each had been in failed relationships and see living apart as a way of making this one last.

Ms. Leslie’s 17-year marriage ended in divorce when her husband left her and their four children. Several years later, she was in another relationship that lasted 14 adventurous years, including nine living together and doing things she had never done, like rock climbing. He left her. She was in her mid-50s. “I never thought I would see the world in colour again,” Ms. Leslie, now 78, said.

Mr. Nieters, 68, came into her life a few years later. A roofing contractor, he had repaired her roof a few times. She invited him to see the opera Madame Butterfly. He agreed if she would go to a dirt track race.

They began dating and have been together for 16 years, though living in homes 35 minutes apart. He lives in the big house that he built on 60 acres in the country, with tractors and a satellite TV for watching sports. She lives in a brightly decorated home with no satellite TV in the college town of Columbia, Missouri.

They talk every day and see each other a few times a week. He comes for dinner and spends the night. Both are content with the arrangement.

“I like living in the country. She lives in town and is really happy where she lives,” Mr. Nieters said.

“He watches tons of TV and I’m not a big TV watcher,” Ms. Leslie said. That might have bothered her if they lived together. She said she has reached the point in life when she realises she doesn’t have to get married or live with someone to be happy or committed.

Still, there’s tension. “You know you’re free but you kind of aren’t,” Ms. Leslie said. “I can’t imagine how it would be without him.” They each wonder, too, what would happen if one got sick and needed ongoing care. Neither has made any promises, although she cared for him after surgery and an injury.

“I think I have doubts about myself and how I would do if she gets sick,” says Mr. Nieters. She told him you never know until it happens.

That’s what Jim Pastoret and Luci Dannar discovered.

They met at a dance eight years ago, he recently widowed and she widowed two decades earlier. He was 87; she was 83. He asked if he could come for tea. She said yes. He did. “The rest is history,” Mrs. Dannar said.

Five years ago, Mr. Pastoret moved from his family home to an apartment 250 steps from hers. He comes over every evening for a supper of fruit and sandwiches. He washes the dishes. She dries and puts them away. They watch the news and “Wheel of Fortune,” holding hands, then go out to the front porch. At about 8, Mr. Pastoret walks home. Each likes their own space. Mr. Pastoret can stay in his pyjamas until noon.

This past year, they have each slowed down with several illnesses. They visited local assisted-living units and talked about moving into one when the time comes, either in the same apartment or in the same building.

“We are very, very committed. He cares for me deeply,” Mrs. Dannar said.

“Without Luci, I would be a very lonesome person,” Mr. Pastoret said.

Write to Clare Ansberry at [email protected]