Is it just me or do gay relationships not last very long?

I've recently entered the gay world for about a year now and I noticed that MONOGAMOUS relationships between 2 men don't last very long (I'm talking over 3 years). The ones that do last long are either open relationships or include 3-somes during . I asked many of my gay friends and guys I dated and they all agree. I want to know your experience with gay relationships. Please don't answer if you never experienced the gay world for yourself.