Old friends and old wines are the best. I totally agree with this. And I'll tell you why.
Russians say: "An old friend is better then two new ones". Of course, an old friend knows you and your habits well, he\she is always there for you, and he\she will never betray you. What about new friends in your life? They probably know you, but they won't understand you as well as your old friend does. I think noone would argue, that friendship is like wine - the older it is, the better it becomes.