I've outgrown friends, and friends have outgrown me. And some friends I've had for the past 20 years, through all of my growing.
Back when I used to go to church, one of the pastors would say that people are in our lives "for a reason, a season, or a lifetime." I think that's wise. I am one of those people who thinks that everyone you have some kind of relationship with is there for a reason. Some people I've had very short friendships with, some people I've had relationships which have turned out very negatively, and like I've said, some people have been with me for a very long time. But I feel like everyone has been there for some reason. Even if it isn't something super profound.