More than a friend, not a couple.

I've been talking to this one person, almost every free moment, of almost every day, for the past 6 years.
We've never had any major arguments. And we both suffer from withdrawal when were unable to talk with each other for more than a few days. We're so close, we seem to read each others minds, going so far as to say the exact same thing at the exact same time.

However, this is not a sexual relation ship, and I don't think either of us wants it to be. Our relationship is free of the demands and social restrictions that a sexual relationship usually goes hand-in-hand with. I don't know what to call this relationship, we are considerably more than friends, but we aren't a couple.

Do you know anyone with a relationship like this? What should I call this relationship?