I asked the "Family Life" class to talk with their friends about what they thought of cohabitation vs. marriage. Since many of my students effectively live together on campus, I thought that many had already voted with their feet in favor of cohabitation. To my surprise, they did not regard living together on campus as real cohabitation, because the couple was not cooking together, or splitting the rent, or responsible for most of the things involved in living in the 'real world' yet.
This is a fair enough distinction. It did give me an idea, though: encourage the couple who are living together to conduct experiments simulating, as realistically as possible, what real cohabitation would be like. They could, say, make all their meals together for a week. They could spend another week really pooling their finances, and facing together what sharing all their costs would look like. They could start interacting with one another's families in a routine way.
Such an experiment might be eye opening.
An important point that we make in the "Family Life" class is that cohabiting is not really the same as marriage.
We could go back one step earlier in the chain to get students to come to grips with the ways in which sharing a dorm room is not the same as cohabiting.
And all of this is in the interest of 'deciding not sliding' into the biggest decision of your life.