Not sure why people do AFK half the time, but even if its to rack up hours, or to check in periodically as you do other stuff on your computer, I don't think its worth the cost.

I've talked with numerous regular users of this game and it seems like the genuine consensus of people that DON'T have this habit is that it really impacts online friendships. If you see someone is on and / or approach them and they're AFK 9 out of the 10 times you see them, at some point you ARE going to more or less give up on them as someone worth talking to.

No one's saying you can't do it, but it will probably long-term impact how much enjoyment you get out of the social dimension of what IS a social game.