The weirdest thing with friends, the way you measure it is if you go without communicating for months at a time, you can sit down and within five seconds be right where you were. I know it's a cliché, but quality not quantity, and that bond will not disintegrate. It does need to be tended to but it won't go away. It's amazing, though - I'm here in New York where my best friend from college lives, and we see each other twice a year and we're right where we were and a lot of it's unspoken.
