They really, really suck. I've been dating my girlfriend for nearly two years. But this summer she moved to a different state, for various reasons. It was temporary, only a little over three months, and afterwards we'd be back in the same area again. But even knowing that it was temporary, and even though we still talked all the time, it was really hard on us at times. I don't know that it would have worked out if it was a more long term situation. I'm really glad it did though.