Do you keep old friends?

I find that as I get older, I cherish my friendship with the friends I've had throughout the years. They've been with me through thick and thin and really know me. Finding new friends would make me feel like I would have to prove something to them just like I had to do when I was in high school! Do you prefer to keep in touch with your old friends from many years back or look for new friends? What is the longest you've had your friends? For me, I've been friends with some for 40 years!