Even if that's your personal experience, that's not what statistics show.
Statistics show that long distance relationships have roughly the same chance of working as any other relationship. Statistics also show a positive correlation between amount of contact and successful long distance relationships, meaning that the more the two people in the couple communicate, through letters, e-mails, phone conversations, visits, anything, the better chance the couple have of staying together (unless it goes too far; don't call her every five minutes, that gets annoying).
The only difference when it comes to ending a long distance relationship is that it is much easier to blame the distance between the two people than it is to pin the actual fault in the relationship. No one is going to say "Well, it's really because I just don't like you anymore, and my new secretary is HOT" instead of "We never see each other, we're so far apart, blahblahblah". This convenience isn't found in a typical relationship, so it is made specific to long distance relationships, which is why when people think about it, most would say that it never works, because many think about why most of these unsuccessful long distance relationships end (or rather, what people who have had long distance relationships say caused the breakup).
The only thing you'll miss out on is sex, unless you have an incredibly long extremity (yes, I made a penor reference, get over it). That and seeing him/her as often as you do, not to mention the physical conduct. But all of this makes for some really fine welcome back events, so be optimistic.Not so uncommon, actually. Since we're talking about statistics, the majority of couples separate before the would-have-been long distance relationship has a chance to even happen. The logic (excuse) being that "it wouldn't work", when really it's most often because one or both of the parties involved would rather not wait for their honey to get back to get their freak on.
Long distance relations can work, if both people involved put some effort into it, just as would be in a typical relationship.