Personally I am against co-habitation. That being said here are a quite a few real life scenarios that I have personal knowledge of:
First couple: Engaged for 2 years, moved in together, 3 months after moving in he left her for another woman he met on the internet
Second couple: Lived together for 6 years, female gets preganant, they get married, separate when child is 1 year old, divorced by time child turned 4
Third couple: Married young (him 21 her 19) never lived together prior to marriage, have 2 children, still happily married 18 years later
Forth couple: Co-habitated prior to marriage (not sure how long) 6 kids and 15 years later they are now divorced
Fifth couple: Living together for the past 8 years, one child (together) female wants to get married, the man doesn't (he won't even look for a job and lives in HER home)
Sixth couple: Living together for almost 40 years(?) never married, have one child together, both are happy
Seventh couple: Co-habitated for 3 years prior to marriage, have 2 kids, still happily married 12 years later
Eighth couple: Co-habitated 6 weeks prior to marriage, have one child together, separated for a few years, reconciled, now living happily together
Ninth couple: Don't live together, been together for 4 years, female wants to be more than "just the girlfriend", man keeps making promises but not backing them up with action, female frustrated, male oblivious
Tenth couple: Lived together for 7 years prior to marriage,no children (together) 2 years after the "I do's" female starts cheating with other married men