When my SO went home last year for summer vacation, he called me up and told me he was feeling terribly strange: homesick, even though he was home from University. We had only been dating (or whatever) for three weeks or so, but I felt the same. Finally we realized: home is wherever we are together. I guess it's when you feel this way, rather than the simpler "fun is wherever..." or "rampaging lust is wherever..." that you know you've really got something.