In ancient Greece, philosophers like Plato and Aristotle were already grappling with the notion of work-life balance. The latter described amusement as a remedy for the “ills of work,” which he said was accompanied by “toil and strain.” Work, they acknowledged, was necessary for living a virtuous life — and paying for stuff — but it shouldn’t be the end, in and of itself.

Nearly two-and-a-half millennia later, we still struggle to define what constitutes a good life and how work and productivity factor in. Our modern-day hustle culture, and many of today’s outspoken business leaders, would have you believe that more is more. A steely, unwavering work ethic is a requisite for success. Sleep can wait, so the thinking goes.

But a growing body of research plus some innovative companies are showing that the truth about productivity is more nuanced. More isn’t always more — but working long hours isn’t always bad either. There are no hard and fast rules.