An old ex-girlfriend of mine once said: I want you to choose, its either me or your friends (because I didn't want her at any of our D&D nights). To which I replied:
"Considering that the average relationship usually does not last nearly as long as good friendships do, that is an easy choice. But I do not think this is an ultimatum where you'll come out as a winner. So you might want to reconsider".
Also,
"Don't ever make me choose between my friends and you, because you'll always lose that battle, and then the relationship is over."
No surprise, but that relationship didn't last very long. But yes, friendships you make early in life, can often last for the rest of your life. They are very important. I made some new friends while in my twenties, through shared hobbies and school. I don't think my age has ever stopped me from making new friends. But friendships are very important, so cherish the ones you make early in life, and stay in contact with everyone.