But from that moment on, Hermione Granger became their friend. There are some things you can't share without ending up liking each other, and knocking out a twelve-foot mountain troll is one of them. Where the friendship began.
I've always thought about relationships this way. If I can't see myself with this person for the rest of my life, I'm not wasting any more time than I need to with them. Simple as that. I have far more important things to worry about right now.