Hey Lost_in_reverie,
Thanks for the great question. This is my first time posting a comment, so forgive me everyone if it doesn't work out right. I have kicked around the same concern about friends in my life. Wondering if others feel the same. Thanks for letting me know I am not alone and it's not just in my head.
My Mom, God love her, has told me more times in my life that friends are just like shoes. We spend a lot of our time looking for them. We try a bunch on reject a lot of those. Find ones we think are the perfect fit, make us feel great, make us sexy, or strong or protected. Ones that we just can't wait to take out in public to show off. But we look in our closet and find piles of them that we never even wear any more. We wonder what we were thinking when we decided "those are perfect". Some of them really weren't a good fit and we knew it when we were trying them on. But all of us have one or two pair that are old, nor really fashionable, scuffed up and a little worn in the soles. (Souls.) But for some reason, they are still our favorite. They just fit, even after all these years.
I think she is so smart.