A couple years ago I was camping in a campsite on Isle Royale and in an adjacent site there was a backpacking couple that clearly and noisily were in the process of breaking up. And, when you are on Isle Royale, you can't leave until your ferry ride takes you off the island, so that unhappy couple was stuck together for at least several days longer.

A friend of mine from college went on a couple month long canoe trip with his fiance and another couple in far Northern Canada where they would not see anyone else for a couple months. At some point on that trip, he and his fiance decided they were not getting married after all. But, circumstances like that meant that they had to share a tent for the rest of the trip.

A couple that are neighbors of mine backpacked the AT several years ago. I do not know if that was before or after they were married, but they have a great relationship and are excellent parents. I suspect in their case, the experience of hiking the AT from end to end made their relationship stronger and lasting.

Good luck.