An important question, and one that transcends the LS. Marriage is a social contract, love is something else again. The attributes that seem to be shared by all happy LS couples that we have run into are two in number: (1) They are in life's adventure together. They always have each other's back. That doesn't mean they don't play hard and play separately. But it means there is never ambiguity about the importance of their primary relationship. Each speaks glowingly of the other. (2) The happiness and pleasure of the spouse always takes priority over their own needs/wants/desires. Compersion rules. Show us that couple, and you have shown us a pair that we want to spend time with.