Different play styles for different people. Person A could play every day for 4 hours and enjoy it. Person B could play every other day and enjoy it. Person C (aka trolls) don't play the game at all and just complain about it. I alternate between A and B.
That's the trick to any MMO, don't play it to the point that it feels like a job. I played Final Fantasy XI for about 5 years, hardcore for about 2 years, and I "enjoyed" it but sometimes I wonder WTF I was thinking spending that much time on a game.