I was on the train headed home from work one night when a couple got on carrying a white loveseat (see above.) They sat on it and rode home, talking like they were in their living room. Guessing by the empty ring fingers, they weren't married. But I'm convinced someday they will be. And they'll probably be married forever.
I'm no expert on marriage and relationships (admittedly, talking to experts all day does not make me an expert) but I think a great way to predict if a couple will last is if they ride the same randomness wavelength, which clearly this couple does. For one adult to say to another adult, "Hey, we should take the couch on the subway!" and the second adult agrees this is a great idea is an indication of odd, odd thought that speaks to the magic between them.