Companies have long trotted out generous paid time off policies to attract talent, some even offering unlimited PTO. And while vacations are vital—allowing employees to vacation around the world or "staycation" around the house—companies often presume that these long breaks will be a cure-all for employee burnout. And this presumption is misguided, as new research from Cornerstone suggests.

Cornerstone, a talent management software company, surveyed 1,000 American workers and found that 87 percent believed three-day weekends relieve stress better than longer vacations. Additionally, 6 in 10 respondents said they actually work longer hours after coming back from a vacation.

Quartz's Sarah Todd wittily sums up the paradox behind vacations from work: "Surely you'll come back to work bursting with positive energy, ready to dive straight back into 12-hour workdays, unreasonable deadlines, an exploding email inbox, and the constant, sinking sensation that you are so hopelessly behind that an important person must already be on their way to come and yell at you."

Todd cites the experience of chef and Momofuku restaurant group founder David Chang, who was told by a doctor to take a vacation to regulate his high blood pressure, according to a 2008 New Yorker profile. He traveled to Costa Rica and came back feeling better… for a while. Then his left cheek went numb, he experienced debilitating back pain, he suffered jaw pain, he lost his hearing in his left ear, and he developed shingles—all because of stress.

Other research has corroborated this anecdotal evidence. In a 2018 American Psychological Association survey of more than 1,500 U.S. workers, for instance, two-thirds of respondents reported that the mental benefits of their vacations vanished within a few days, and 49 percent said they returned to an even more taxing workload. It's no wonder that workers leave so much unused PTO on the table every year.

Clearly, it's time to complement conventional time off practices with new strategies for avoiding employee burnout—and the four-day workweek does indeed seem like a promising place to start. We previously covered the case of Perpetual Guardian, a New Zealand financial services firm that test-drove a four-day workweek before making it a permanent option. And earlier this year, a study of Perpetual Guardian employees who worked 32 hours a week instead of 40 hours (while still being paid for five days of work) found that those employees were 20 percent more productive, were 7 percent less stressed, and experienced a 24 percent improvement to their work-life balance. Plus, founder Andrew Barnes noted that team engagement increased an average of 20 percent.

Still, as we noted before, it's important not to force employees onto the same schedule or even the same flexibility policy, since one-size-fits-all solutions are a myth. The key to companies implementing flexibility the right way—and enjoying the maximum boosts to engagement, productivity, health, and happiness—is to provide a range of flexibility options. Some people might want a four-day workweek. Others might opt for an earlier or later work shift, or to work across different dayparts with breaks in between. Others might need part-time work. And then there are all the location-based workday modifications. The point is, narrow-scoped flexibility policies will re-engage burnt-out employees as little as long vacations do. But when you offer a range of flexibility options—alongside traditional vacations—employees are happier, healthier, and even more efficient.