I really disliked the assumption that "of course, sex dies in a relationship after 2 years." I just find this such a silly statement! Lots and lots of partnered people still desire their partners after 2, 5, 10 or 20 years.
Yes, NRE dies. As it must and should. But sexual desire is not just based on newness. It could be based on love! Imagine that. Sexual desire can wax and wane in a LTR, of course, but that doesn't mean it's dead, never to be resurrected again. It's just sleeping!
And even if your sexual desire for your mate does die after 2 years, does that mean the next inevitable step is, "Well, Ima go get me some strange, behind my loved one's back"?
Maybe that works for undergraduate "men," ie, people with the emotional abilities of a gnat. For people with a skosh of maturity, I do not think cheating ever should be the socially accepted default after 2 years of a relationship.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
Mags (poly, F, 61) loving miss pixi (poly, F, 39) since January 2009, living together since 2013
"Master," (mono, 34), miss pixi's Dom for 2 years