It's nice to have friends from different periods of your life. You can reminisce about times you shared together and talk about current happenings without fear of judgement.
I guess I'm lucky to have this type of friendship with various groups of people. Although we don't see each other every day or as often as we'd like to, we always manage to remain good friends.

Maybe making friends when you're a kid is easier than when you're an adult due to the pre-judgement factor. For instance, when you're a kid you like to play a game as your classmate then the two of you become friends.