Never happened to me, but my best friend was away from her boyfriend all summer. They talked almost every day on sites like Stickam and MatchVenue (they thought it would be more fun than Skype) and they managed to pull it off.
I guess it's all about knowing your limits. You can pull it off for a while, but eventually your body will cave in. All you need is some time off, detach yourself from all the academic work and recharge your batteries.