My husband escaped the cult of 24/7 early — the night he saw his boss tip-toe out of the office (afraid he’d be seen as a slacker for leaving early on his kid’s birthday.)

Good process, investing each minute well. Those things create more value than dutifully staying late, my husband explained years later. He had little patience for my more standard view — that working long hours and being on-call were just part of having a good job.

The latest Harvard Business Review says I was wrong and my husband is right — that normal “always on” work culture produces inferior results.

Harvard Business School professor Leslie Perlow ran experiments at Boston Consulting Group over four years showing this: Teams that got predictable time off produced more value for clients compared to standard teams who were “always on.”

BCG – the management consulting giant – ran these time-use tests on real-time assignments to see if there was a way to maintain excellence while giving employees predictable and required time off every week. In one experiment, a BCG team mandated that each consultant (on an important project with a new client) work only 4 days a week — each teammate sat out one standard workday while the project proceeded smoothly without him/her. In others, consultants were required to unplug and abstain from work (no email, no cell phone) after 6pm one evening per week.

Clients were happy with results and scores of employee development, communication, job satisfaction — and, oh, work/life balance – all jumped in a statistically significant way.

How could this be?

It turns out that if you know you’re required to switch off at 6 on Tuesday, you’ll think much harder about a lot of things. Like how to do what’s essential before that time, how to triage things that are less important, how to communicate to your colleagues what they need to know so you can hand off when you switch off.

Teamwork — sharing and passing information — also improves by necessity. Forced to communicate about what they were doing and how they were doing it, the consultants found process improvements, anticipated problems, and produced better results for clients.

The article, “Making Time Off Predictable–and Required”, is $6.50 on the HBR website and is sure to create lively conversation at the office. And for more on what we can each do in our own lives, check out our BusinessWeek piece “How to Excel at Your Job and Be Home for Dinner”.