Sometimes Jeff Mattson describes it as “the doldrums” — the gloomy period he endured last winter after retiring from the U.S. Postal Service.

He had been delivering mail for 31 years. He liked his co-workers, enjoyed the work, was good at it. He recalls those days — even the day he delivered mail in an 80-below windchill — with fond humor.

But he was fully vested in the Postal Service’s pension plan. So he retired last August, just after turning 62. Over the fall, he kept busy doing home-maintenance projects at his daughter’s house in Iowa and his own in Dayton.

Then came winter’s cold, empty days.

“Oh, it’s boring, I’ll tell you,” Mattson said. “I putzed around. Watched reruns of ‘Gunsmoke’ and ‘Bonanza’ … It was wearing on me — physically wearing on me and psychologically wearing on me. I just felt I wanted to do something.”

So he found a job. Two jobs, actually: mowing a golf course and bartending at Target Center. Now he has things to do and places to be, new friends and new experiences. The work pulled him out of the doldrums.

“You get peace of mind and satisfaction knowing that you’re actively doing something,” he said. “You’re useful. You’re still a part of the economy, instead of just locked in the house.”

Mattson’s feelings about working versus “putzing around” would not surprise the economists, authors, academics and journalists who gathered in New York City last month to discuss the future of work and retirement at Age Boom Academy, an annual workshop at Columbia University.

“Once people are out of work, almost 85 percent say they would like to return to work,” said Ursula Staudinger, a Columbia psychologist who focuses on life span psychology, speaking at the event. While still employed, people tend not to appreciate the benefits of working until “after we have that vast time of private life and leisure,” Staudinger said. “If all of our life is vacation, vacation loses its value.”

Restructuring retirement

The message was emphasized repeatedly throughout the three-day workshop: Work is often beneficial for physical, emotional and cognitive health. It also, contrary to widespread misconception, is good for the economy, contributing to a more productive workforce, with more people paying taxes and fewer drawing Social Security.

“We need to keep people in the workforce because it’s good for their heads, it’s good for their body, it’s good for their checkbook, and it’s good for the Social Security Trust Fund,” said John Rowe, a Columbia professor of health, policy and aging. He’s also former CEO of Aetna, one of the country’s biggest health-insurance companies.

These days many people consider working longer simply because they can’t afford to retire. The widespread shift in retirement financing from traditional pensions to defined-contribution plans like 401(k)s has left many Americans without sufficient savings to support themselves for the decades ahead — and Americans who reach 65 have, on average, another 19 years of life. By working longer, they can increase their savings and postpone claiming Social Security, which boosts their benefits by 8 percent for every year they hold off up to age 70.

Indeed, labor force participation at ages 65 to 69 has increased at a greater rate than had been projected by the Social Security Administration, said Gary Burtless, an economist at the Brookings Institution in Washington who has written numerous books on economic aspects of retirement.

Of course, some people are unable to keep working — because their health is poor, because they’re caring for an older or ailing relative, or because their jobs are physically taxing or otherwise unpleasant.

But for those who can do it, speaker after speaker at Age Boom Academy emphatically recommended it.

“I think having a reason to get up in the morning and having activities that matter in the world are the No. 1 thing that keeps people well,” said Linda Fried, dean of Columbia’s Mailman School of Public Health and former director of geriatric medicine at Johns Hopkins.

Some speakers called for dramatic societal changes that would reshape work, education and leisure around life phases or circumstances rather than age.

That might sound far-fetched in the current political climate. Marc Freedman, author of “The Big Shift: Navigating the New Stage Beyond Midlife,” noted that neither presumptive presidential candidate has presented compelling ideas in this area. Yet both candidates clearly believe in working well past traditional retirement age, even when performing what’s ostensibly the most important job in the world. Donald Trump is 70, and Hillary Clinton turns 69 in October. And whichever one is elected would be either four or eight years older when their presidency ends.

“It’s high time to collectively start a discourse that aims at the restructuring of work and retirement in the 21st century,” Staudinger said.

Changing nature of work

Such a restructuring would only be the latest of changes in the nature of work and retirement over the years, the experts noted.

Around the turn of the last century, work was more physically demanding and often more dangerous. Retirement essentially didn’t exist, said Courtney Coile, an economist at Wellesley College who spoke at the workshop. People worked until they died or their health gave out.

In 1935, when the Social Security program began, the average American life span was 61. Now it’s 78.

Most people are capable of working longer than they do, Coile said. Among people ages 55 to 59, an additional 3.6 percent could still be working. That percentage rises with age — nearly 40 percent more people in their early 70s could be working than do now.

The greatest benefits come, predictably, from enjoyable jobs — jobs that are flexible, provide some autonomy and give people the feeling that they’re valued and making a positive impact, said Nicole Maestas, an associate professor of health care policy at Harvard Medical School.

Richard Johnson, a labor economist and senior fellow at the Urban Institute, said evidence suggests more people are finding post-retirement jobs that are less stressful and demanding than their pre-retirement jobs — albeit at about half the pay.

Jeff Mattson is earning less than half of his Postal Service pay now. But he doesn’t mind.

“The feeling of self-worth augments your income,” he said.