If you want to know when you can retire, the internet is happy to offer you a million financial calculators. What few experts or articles will ask, however, is whether you should retire at all. Not author and neuroscientist Daniel Levitin.

On the TED Ideas blog recently, he skipped succession planning and 401(k)s and instead urged those in the later decades of their careers to plan to work forever instead.

"I interviewed a number of people between the ages of 70 and 100 in order to better understand what contributes to life satisfaction. Every single one of them has continued working," he insists.

Golf or gardening isn't enough.

And when Levitin says working, he means really working, not keeping yourself occupied with golf or gardening.

"Too much time spent with no purpose is associated with unhappiness. Stay busy! Not with busy­ work or trivial pursuits, but with meaningful activities," he advises before reeling off a list of successful icons who have continued to work into their 70s and 80s, from the Dalai Lama to author Barbara Ehrenreich (not to mention the entire remaining presidential field and a few members of the Supreme Court).

He's not the only one making this radical suggestion. Stanford psychologist Laura Carstensen argues that we arrange our careers entirely wrong for the rhythm of our lives, forcing people to cram together their most productive professional years and raising small children, and then leaving them with too little to do in their later years.

"Rather than a four-decade professional sprint that ends abruptly at 65 ... we should be planning for marathon careers," Quartz explained. What would that look like? A lot like Levitin's endless work: combining training and apprenticeships with having kids in your 20s and 30s, and then a full career that starts at 40 and ends perhaps around 80.

Businesses should help seniors stick around.

But, wait, you might respond. These experts are masochists. I don't want to be working like a dog when I'm 75. Both would respond that you have a point. While these scientists might advise against full retirement, they also say most older folks will want to change their schedules as they get deeper into their golden years.

The aging icons Levitin mentions, for instance, have all "modi­fied their work schedules to accommodate age-related slowing." Companies should do more to help their senior team members keep working by allowing them the flexibility to do the same. Whether that means shortened schedules or the freedom to nap without judgment, making space for older workers is a win for businesses.

"Corporate culture in the U.S. has tended toward ageism," he says with understatement. "Employers should recognize that offering oppor­tunities to older workers is smart business, and not just a feel-good, charitable act. Multigenerational teams with older members tend to be more produc­tive; older adults boost the productivity of those around them, and such teams outperform single-generational ones."