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While there are all types of employment perks that are getting attention, from free food to on-site barbers, flexible work hours is by far the most appreciated gift an employer can extend to an employee. 

A survey of U.S. adults by Modis, a tech staffing firm, found that more than 50 percent chose flexible hours as the most important work perk. That came way ahead of unlimited vacation time, which came in second at 21 percent. Long-term paid parental leave came in a distant third, at only 8 percent. 

“People are happier when they are able to take care of things when they come up,” Jack Cullen, president of Modis, told CNBC. “I think employers are recognizing this is real and (flexible hours) is a way to really attract and keep people.”

In the midst of several high-profile tech companies announcing radical vacation and leave policies, Modis has been emphasizing the importance of encouraging employees to relax.

In a report it put out this summer, Modis urged people to “unplug” entirely during vacations. That means no computers, smart phones or tablets on the beach. In particular, employers shouldn’t let workers have access to work email during vacation, argued the firm. It even suggested that the whole business should shut down for a week or two around the holidays — especially if work is already slow during that time. 

But despite the benefits of work that accommodates people’s personal lives, U.S. workers have certainly not lost interest in money. Sixty-one percent said they’re willing to relocate to a different part of the country for a job with better pay. Of course, there are different opinions on how much of a raise would justify a move. More than 85 percent said they would expect a raise of at least 20 percent, while half would want to see a raise of at least 30 percent. 

But Americans are split on whether they’re getting enough money at their current job. Thirty-six percent say they are paid enough for the job they do, 37 percent say they are underpaid and 27 percent are unsure.