On a blog for the Wall Street Journal (where else?), Emily Oster gives advice based on economic theory. For example:
There is a model in economics called the “sS” model. It’s not often applied to relationships, but I think it should be….If something really good happens, or many good things in a row, it pushes you over some threshold (this is the “S” threshold) and you get married.
It’s not exactly Dear Sugar, but Oster comes up with some sound advice anyway.