I found this study when I was researching that couples that live together for 4 or more years actually have a higher percentage of staying together. Maybe the key is to date long enough to really know.
I want to reiterate I don't think it's wrong to cohabitate before marriage. Bottom line, I think it should be your own decision. You shouldn't have to do anything- one way or the other. Don't just do it because everyone around you is, do what's right for you.