How do your characters speak to each other? It could make a difference in how long they stay together. Lots of writers — not just of romance novels — have demonstrated an instinctive understanding of this in their work.
This long-read from Atlantic talks about research into couples’ behavior, but about half-way in you’ll find four categories of talk to apply to your characters.
Masters of Love – Atlantic Mobile
http://m.theatlantic.com/health/archive/2014/06/happily-ever-after/372573/
sharon p. lynn 