Re: Living together before marriage. Yay or nay?
NPR did a segment several months ago about the cohabitating thing- the rates are higher for couples who cohabitate if they go into the cohabitating for "testing it out." Couples who go in with clear expectations (short term or long term) had rates similar to married couples.
It would seem solidifying what you two are expecting out of a relationship is a bigger factor than cohabitating.