A Relevant ArticleThough rather simplistic, in my opinion. The comments are interesting, however: http://www.nytimes.com/2012/12/02/opinion/sunday/new-love-a-short-shelf-life.html?src=recg&_r=0.
To me it's just yet another nail of monogamy. Everyone wants and needs variety! And if you are honest and open about it, and collaborate on how to achieve it, I don't see a problem.