For me:
I've been gone for over 2 months & planning to go back(after I fix myself a new pc). Main reason I wanta return's not really the game itself(its a great game, but there ARE same if not better ones out there), but the friends I have made.
Sure, I can make new friends anywhere, but would hate to leave old friends behind. The day I really quit FF11 will be the day all my buddys are gone or we move to a new game as a group.
just my 2 gils~