There has been a lot of research about the optimal duration in a health-care setting, such as a hospital.

WSJ: Hand-Washing Techniques for Good Health

Now Major Peake, as he waits to be assigned a space mission, is in an ongoing programme of spacesuit training, zero-g flights to "practice weightlessness" and 12-day stints 20m (65ft) under water to research "crew behaviour for long-duration missions".

BBC: Major Tim Peake says he is not too old to go into space

The long held belief that adults who are unable to quit smoking is ultimately related to duration of smoking may potentially be replaced by such research showing that there are specific genetic factors which could influence teen smokers to become heavy smokers throughout their lives.

FORBES: Genetic Factors Linked to Smoking Addiction in Teens

But Morningstar and other research firms caution that anyone planning to hang on to Facebook for a longer duration might want to step back from that frenzy and give the deal some thought.

WSJ: IPO Analysts Warn of Longer-Term Facebook Risks

Research demonstrates that red light problems at intersections can be corrected simply by extending the duration of the yellow light a second or two.

FORBES: OUT OF FOCUS

And a long duration living and working in space is what the Space Station is all about -- to do the research and the science necessary to take us beyond Earth orbit.

WHITEHOUSE: President Obama's call to the International Space Station

The Dow Jones Industrial Average has experienced around 20 bear markets, averaging a duration of one and a half years from top to bottom, says James Stack, president of InvesTech Research, a US-based market tracking firm.

BBC: Explaining a bear market