Therese-Heather Belen is living the dream, working remotely full-time while traveling across Vietnam, Thailand, Japan and India.

But the dream comes with a catch: Her workday starts in the evening and lasts through the night. To stay in the same timezone as co-workers at her New York-based marketing tech firm, about a 12-hour difference, she works and takes meetings into the wee hours of the morning.

For some, ambitious “workcation” trips like these are seen as a way to make up for lost time during pandemic lockdowns. For others who choose to wander far from their home time zone, such adventures can veer off course, becoming hellish journeys to the land of sleep deprivation.

Belen, who is traveling with Remote Year, a program that functions like a kind of study abroad trip for working adults, said this lifestyle allows her to experience more of the world than would ever have been possible working a traditional 9-to-5. “You hear stories all the time like, ‘I went skydiving before I started my workday,’” she said.

Remote workers and socalled digital nomads have logged odd hours from hotspots like Bali and Goa long before COVID-19. But the abrupt shift to remote work during the pandemic pulled what was long an idle fantasy for many into the realm of the possible. Almost 17 million U.S. employees describe themselves as digital nomads, more than double the pre-pandemic number, according to MBO Partners, a firm that connects companies with freelance talent.

The trend of longer work-leisure trips has accelerated as pent-up demand for international travel has boomed after years of restrictions. That’s giving some digital nomads a bad reputation for driving up prices and trampling local culture in popular vacation destinations, but it hasn’t slowed them down. Dozens of countries are marketing a new class of visas to these professionals to compete for tourism dollars. And despite many highly publicized return-to-office announcements in recent months, some degree of remote work remains a fixture at most companies.

Many remote workers who have decamped to far-flung locales will, like Belen, work a split shift, logging on for a few hours in the evening through midnight, before taking a few hours to sleep and then waking up to log back on for another round.

And it works, to a certain extent. Her mom was a labor and delivery night shift nurse, so the idea of sleeping during daylight hours didn’t strike her as outlandish. She’s usually online with coworkers until 1 a.m. or 2 a.m. and then sleeps in until 10 a.m. or so before waking and catching up on emails. But because her job revolves around meetings, she’s sometimes on call at all hours. “Tonight I do have a 3:30 to 4 a.m. meeting that I have to be on,” she said. “So I have many, many alarms that are set for the most random hours for me to jump on that meeting and then just fall back to sleep after.”

Some, like Belen’s partner, a software engineer, have an easier time with time-zone differences. That’s because their jobs are less meeting-heavy and more open to asynchronous work, so they have more flexibility to get things done on their own schedule.

Tue Le, chief executive officer of Remote Year, estimates that somewhere around 15% of program participants traveling in Asia keep strict U.S. hours by staying up overnight. Roughly another third work flexible hours with a mix of evenings or early mornings to collaborate with coworkers back home.

The graveyard shift can work for those wired to stay alert deep into the night, said Ilene Rosen, a sleep medicine professor at the Hospital of the University of Pennsylvania. But for many others such schedules go against ingrained circadian rhythms, making it challenging or impossible to get enough sleep. As anyone who has had to get up early and go to work after a terrible night’s sleep can attest, it can drain energy, zap concentration, and undermine emotional regulation. The bottom line: Consistently pulling all-nighters is generally not a good idea for optimal health, let alone top work performance.

“The science as we have come to understand it over the last 20 years indicates that while it may be exciting, and that it may be even doable for some short period of time, it isn’t great for our bodies,” Rosen said. Studies have found longer stretches of night-shift work have been associated with more serious health consequences, like heart disease and cancer.

Even with the best practices, the night shift can be punishing — and isn’t for everyone. After two months, Belen’s sleep schedule has been completely thrown off. “I would say I’m struggling — everyone I know is struggling to some extent.” Some people she’s met while traveling have had to quit their jobs. Others have had to cut back their hours. One person she knows was fired. Often, she said, the inescapable truth is that some people simply are less available — whether they want to be.