I'm originally from Littleton, Colorado. I met my best friend, Becky, when I was thirteen. We've been best friends for almost eight years now, and I've lived in New York for six of those years. We live more than 1800 miles away from each other, and I've learned so much about love, life and friendship just from having her as my long-distance best friend.
When you have a long-distance best friend, you experience things a little differently than those in an average friendship would. You and your BFF have the opportunity to watch each other grow, without growing apart. Being far-away friends means you can watch them thrive and flourish and shine from a distance, without experiencing the sometimes undesirable effects of a friend changing and finding who they are. So many friendships fall apart because one person has a crazy schedule and can never make plans to hang out. When your best friend lives across the country, you don't really have the opportunity to hang out, so it doesn't affect your friendship. On the other hand, when you two are separated by miles and miles, you're bound to appreciate the time you do spend together a whole lot more.
Being across the states also means probably being in different timezones, which in turn means that the times that are convenient for her to call you might be the least convenient times for you to talk. As frustrating as that may be, it helps the both of you to acknowledge that friendship is a two-way street, with communication being the most important road signals. She calls you when she's driving home from work, and you still pick up even though you're getting ready for bed. You call her when you have a break between classes for lunch, and she still picks up even though she hasn't even gotten out of bed yet. It isn't convenient, it isn't easy, but you'll always make the time for her.
The fact that she's far also gives her an advantage in the advice situation: she might not know your friends, or your enemies, or your significant other, or whoever it is that you're arguing with, and she can therefore provide you with a truly outside perspective and unbiased (well, as unbiased as a best friend's could be) opinion on how to handle things.
The strength of your friendship has been tested in every way possible: time, distance, lack of time spent together; regardless, you would do anything for her and wouldn't change her or your friendship for the world. She'll be your maid of honor and the godmother of your first born child, and most importantly? Wherever you are in the world, no matter how old either of you get, she will always be your best friend.