At Seer, a digital marketing firm in Philadelphia, employees work hard to get job done—and are rewarded with extra time to play.

Seer's unlimited paid vacation policy has given employees the opportunity to explore such activities as backpacking through Europe, saving sea turtles in Costa Rica and preparing Thanksgiving dinner for 40 people at home.

"It's about allowing people to do things that make them happy," said Crystal Anderson O'Neill, Seer president. "It's about being productive, being fresh, being your best self."

While less than 2 percent of employers currently offer the benefit, more companies are introducing the concept of unlimited vacation, according to the Society of Human Resource Management, a nationwide trade group.

The model was born at Netflix, LinkedIn, Hubspot, Evernote and others startups and is making its way into mainstream corporations. In 2015, General Electric uncapped vacation days for 30,000 of its senior salaried employees.

There's something in it for the company, too. Abolishing standard vacations means employers do not have to pay workers for unused time if they get laid off or quit. (Some companies, including Seer, offer unlimited vacation in addition to standard vacation time.)

Removing the lid from paid time off doesn't mean employees keep a packed suitcase next to their desks. There are guidelines. At Seer, the first annual round of vacation is limited to 15 consecutive business days. Team members must be back in the office for 30 days before becoming eligible for another15 days of vacation.

Time off must be approved in advance by a manager, and workers requesting vacation days are responsible for ensuring there is adequate coverage to fulfill clients' needs in their absence.

"We are all adults here," O'Neill said. "It's up to us to make sure the job gets done."

At Seer, the least amount of vacation time logged by an employee in 2015 was 3.35 weeks, a couple days more than the three weeks of vacation that is the company's standard benefit. The most vacation time taken by an individual was 8.2 weeks.

In addition, the company has 12 paid holidays. And from Memorial Day to Labor Day, the staff has the option of knocking off work at 1 p.m. on Fridays, provided there is no work left undone. The business is officially closed the week between Christmas and New Year's Day.

"We ask that everyone put in a few hours wherever they are, at some time during the holiday week, but it is not mandatory," O'Neill said.

Throughout the year, employees can, with a manager's approval, take advantage of such flexible options as shifting office hours to working from home.

"You don't necessarily have to take a day off if someone is coming to your house to fix the cable," O'Neill said.  "You can take care of clients from home."

The unlimited vacation policy has been in place for three years at Seer. So far it hasn't made a significant impact on employee retention, although O'Neill notes the company is experiencing other positive outcomes. Client satisfaction is high; Seer is growing and currently is in hiring mode.

"We believe it's a valuable benefit and the right thing to do, even if we haven't seen a dramatic difference in turnover," she said.

Other companies are taking creative approaches to time off, as well.

At TMNAS in Bala Cynwyd, a provider of support services for insurance companies, new parents can take 12 weeks of leave.

New parents receive an additional bundle of joy, said Sarah Naraghi, TMNAS human resources director.

"Any of our employees who work 30 or more hours a week receive 10 consecutive days of extra paid time off in the first 12 months after a birth or an adoption," she said.

To ease the transition from home back to the workplace, employees can work three- or four-day work weeks for up to 20 weeks, "which helps a lot in terms of adjusting to their new normal."