From world cruises to multi-country land tours, travel experts are touting the benefits of long-haul trips – here’s how to tap into this niche. Optimal vacation length has been a point of contention for more than a century.

Former U.S. President William Howard Taft identified the ideal amount of time off to be between two and three months per year. That length of time, he noted in a 1910 article for The New York Times, is “necessary to continue work the next year with that energy and effectiveness which it ought to have.”

Meanwhile, a 2013 study from The Journal of Happiness Studies, a peer-reviewed scientific forum covering the state of happiness and well-being, reported that long-term vacationers (those who spend an average of 23 days away) experience optimal levels of health and wellness on the eighth day of their time off.

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