Here's an interesting article, no reason this wouldn't be true about men in polyamorus relationships too:
Polygamy is key to longevity!
ANI Mar 6, 2009, 12.00am IST
(Want a long life? Get a second…)
Forget long walks and calorie-controlled diets, the sure shot way to live a longer life is: get a second wife. That's the conclusion of a new research, which has suggested that men from polygamous cultures outlive those from monogamous ones. After accounting for socioeconomic differences, men aged over 60 from 140 countries that practice polygamy to varying degrees lived on average 12 per cent longer than men from 49 mostly monogamous nations, says Virpi Lummaa, an ecologist at the University of Sheffield, UK.