I have a couple friends and the three of us were friends in high school. Now we're 63 and one's in Arizona and one's down in Georgia and we don't get together or even send cards much but I know I could show up on either's doorstep and be welcome/helped or could call them, etc.

Most of my "former" friends like that I'm friends with on Facebook along with cousins, siblings, etc.; I think that's what Facebook is good for, making sure you can get in touch if you feel you need to.