It's not the leave you take, but what you take when you leave that matters most.

More and more, companies are offering sweetened leave policies. Put aside parental leave, which has its own set of rules and has evolved already from corporate perk to de rigeur offering. Also, let's not think of programs like a "paw-ternity" leave, where you get time off for getting a new pet.

Think instead of the recent trend of companies encouraging employees to do someting to recharge their batteries. Most executives encourage the occassional mental-health day, but more corporations are offering a full-blown sabbatical. Genentech, for instance, gives you a six-week sabbatical after six years of service, while Adobe gives you a month after 10 years.

The idea behind a sabbatical or paid leave of absence is that, once loosed of the shackles of worklife, you will return a happier, more creative and more productive worker when you return to your cubicle.

But is that true? There has been very little academic research about productivity effectiveness in relation to sabbaticals in the corporate world. Academia, which made sabbaticals mainstream, has pumped out a ton of research on why they're the best thing ever, but one wonders about confirmation bias. Professors who get to take a year off every few years think taking a year off every few years is a wonderful idea.

Instead, most of the positive benefits for companies are more anecdotal. That's not surprising, because improving the productivity and creative juices of the affected employees isn't the only endpoint. Just offering a program like this is seen as the kind of employee benefit every company needs nowadays to attract and retain the best talent. There's little downside for a startup to offer it, particularly since most won't survive long enough to make good on the promise. But small business and large corporations are competing in the same talent pool, and flexibility in the way you allow people to work is a key benefit.

If I had to take this as a bet to Gulfstream Park, I'd wager that most companies will be increasing sabbatical programs in the coming year, or at least get more generous with smaller-scale leaves. (Millennials and Gen-Xers alike expect them, apparently.) But, my hope is that there's more thoughtfulness about these leaves so that companies can get a more measurable benefit from letting employees wander off from time to time.

Related: How You Can Recharge Your Entrepreneurial Batteries With a Working Sabbatical

To that end, there should be two "takes" for every leave:

Employees have to take an action plan with their leave.

Constraints are great for creativity, but one of the big question marks with most sabbaticals and leaves is the open-ended nature of them. Like a boomerang, many companies send folks on their way, with the only expectation being they return at the end of the trip. Why not set a higher bar by setting expectations for what you expect from the employee when she returns?

It doesn't have to be homework. In fact, it shouldn't be. But companies should take advantage of the temporary separation by having the creative juices the break is supposed to elicit start paying off right away. For instance, if a company has a pain point, why not task an employee to spend some time thinking through the solution? A month with new scenery, fewer work-related distractions and a decreased stress level could spark the kind of innovation to get around a particularly problem faster and more effectively than a bunch of folks brainstorming in a conference room.

Related: How to Turn an Underperformer Into an Ideal Employee

Employers have to take an opportunity to test the rest of the team.

When Intel launched its own sabbatical program, believed to be the first of its kind in corporate America, back in 1981, it did so not just for employee rejuvenation, but also for employee evaluation. Because other people will have to take up the work of the employee on leave, it's a great opportunity to see how other employees respond.

That evaluation can happen in two ways. First, you can check attitude. Are people resentful that a colleague is off for that long, even if he was entitled to the time? Are people complaining about additional workload that's not normally in their scope? Those are pretty good red flags for employee assessment.

But you can also expose team members to new challenges and see how they respond. If someone in sales takes a month off, it might be worth taking a promising person from the back office, who never had a client-facing position, and seeing how she responds.

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Or, you can use it in your internal succession planning. Rarely do you get an opportunity to see how deep your bench really is, but the sabbatical of an executive gives a great laboratory to see how certain people respond when they rise up the ladder.

One way or another, there has to be an intention inherent in the employee taking the time off and an intention in the employer allowing it to happen, beyond anecdotal evidence that the leave period will somehow help the company. Whatever you do, just don't leave a leave alone.