There's a certain glamour to burning the candle at both ends, living fast, working ridiculously hard, playing hard, and, perhaps, burning out young.

And it doesn't just apply to rock stars. It affects plenty of business owners too.

Sure, you know pushing your employees to work 60-plus hour weeks or to continually create without recharging their brains isn't sustainable, but perhaps you're calculating that the short-term gains from this big push will make up for the reduced productivity or staff-turnover costs down the line.

But if that's what you're thinking, according to new, in-depth research your math is wrong. The Towers Watson 2012 Global Workforce Study looked at 32,000 employees across 30 countries to see how engagement affects productivity (and profits) over the long haul. The HBR Blog Network summarizes the findings:

This new study concludes that the traditional definition of engagement--the willingness to invest discretionary effort on the job--is no longer sufficient to fuel top performance in a world of relentlessly increasing demand. The problem is that "willing" doesn't guarantee "able."

What's required now is something called "sustainable engagement." The key factor, the study finds, is a work environment that more fully energizes employees by promoting their physical, emotional and social well-being….

In a broader analysis of 50 global companies, Towers Watson found that companies with low engagement scores had an average operating margin just under 10 percent. Those with high traditional engagement had a slightly higher margin of 14 percent. Companies with the highest "sustainable engagement" scores had an average one-year operating margin of 27 percent.

Forty percent of employees with low engagement scores said they were likely to leave their employers over the next two years, compared to 24 percent of traditionally engaged employees, and just 18 percent of employees with the highest "sustainable engagement" scores.

To put in it simple terms, working your team flat-out until they fail is going to hit your bottom line. Hard.

It's far preferable over long-haul to help your employees create balanced, sustainable lifestyles for themselves. 

How do your foster this sort of healthy, sustainable engagement? Simple things, according to the HBR write-up. A comfortable work environment that encourages healthy living obviously helps, but nothing is more important than decent and humane management: "No single behavior more viscerally and reliably influences the quality of people's energy than feeling valued and appreciated by their supervisor."

Helping employees balance work and life demands also ups sustainable engagement. "Policies focused on flexibility and working remotely contribute to a more energized workplace," says HBR, "and so does setting organization-wide boundaries around the length of meetings and the hours during which people are expected to respond to email."

Looking for more ideas on how to keep employees happy and therefore engaged long term? Morgan Norman, the founder of social performance management application WorkSimple, sent some suggestions. Norman agrees that flexible schedules are key but adds this advice:

1. Be clear and transparent.  If your employees aren't aware of organizational news, team shake-ups, and how they need to operate, don't throw it in their face when they are going in the wrong direction. Be clear and transparent with what you expect from them.

2. Real-time feedback.  Offering employees real-time feedback helps employees with their individual goals. This gives employees the answers they need now, rather then later (you don’t want them going down the wrong path unknowingly, do you?). Don’t wait till yearly or quarterly performance reviews to offer advice and direction.

3. Encourage strengths.  Say you have a star performer who's great at hands-on presentations. Don't stick them in a back room and have them only work on preliminary research. Rule of thumb: if employees are doing work they're passionate about, the output will probably be positive. Encourage their unique strengths.

Could your employees keep up with your current pace of work over the long haul? Is this something that worries you?