I just have a little big question... Why don't you simply kick off the game people that are away from keyboard from some time...?
That is... it's pretty convinient to log in and go to work leaving the game be for 8h or so... During this time you are not doing anything in the game (beside making presence), other people that actually want to play the game and not use it as a parking lot can't log in because some person loves to spend electricity and leave the game on for no purpuse (that is, no gaming purpuse).
I'm sure if players that are more than 45min in afk were kicked there wouldn't be a great load in the serveres. Well, just me thinking, of course.