Infatuation versus love

How can you really tell one from the other?  Note: infatuation is not always before you get together with someone.  It can go on well into the relationship.  I have seen this happen many times before, and couples who had been together for years before either of them knew that they did not really love each other.  Also note: Infatuation is not always a bad thing.  It just becomes a problem when you confuse it with love and will not be convinced otherwise.