Wow, what an interesting thought exercise. I have never ever thought of this before. However, if marriages were time-limited contracts, then I guess the vow of "'til death do us apart" kind of loses its meaning, no?
Prayers do make a lot of difference in Changing your partners behavior.
And also, I consider myself somewhat religious but I really don't think prayer has much effect on other people's thoughts, behaviors or patterns. Nor does prayer do anything with someone's well-being or health.
As I get older, the more I realize that people rarely, hardly change, especially as they get older.