Cohabitation is subversive and I'm only feeding the statistic that cohabitation before marriage is not a good indicator for marital longevity.
Discussion
Correlation vs causation again though bro.
I dated, and cohabitated with, a girl on and off for four years. Whenever I was thinking about proposing to her, she'd do something crazy and/or break it off. And then change her mind within hours.
Some extended cohabitations (and extended engagements) are because one or both of the parties are not sure it'll work as a marriage.
I'm not the one figuring it this statistics, and even if it is just correlation, it was true for me.