I don't have many close friends, but the ones I do, I'm fortunate that they're all people whom I can go for literally years without seeing, and we always pick up right where we left off. Nothing awkward, nothing uncomfortable, just like putting on a broke-in favorite pair of tennis shoes. It's not that their life hasn't changed, and in my case it changed quite drastically sometimes. But the stuff that counts the most--the people we are inside, our interests, memories of our favorite times together--doesn't change.
But that probably goes in the happy thread.