You never lose your friends. FFL is true. BFF sometimes changes but what happens is a pretty awesome thing:
You don’t need constant contact once you’re friends with someone. You can _not_ see them for days, weeks, months, years, DECADES…
…and you’re still friends.
You may not be into the same things anymore, but once friendship is formed, it sticks. You don’t have to do everything together – so BFF *can* be something that goes away – but FFL is a truth in life.