I just play until it is no longer fun to play the game anymore. I absolutely despise the incorporation of achievements into the video game world so if I happen to get one, good for me, if not oh well. Usually if I lay off on a game when it no longer becomes fun I will be able to pick it up again after a few weeks and finish it. That was the case with halo. I played and played, but got burned up really quick on multiplayer because I got stuck in games with eight year olds who would literally scream as loud and as highly pitched as they could the entire match into the mic. When I would mute them another one would kick in and then on top of that I got stuck in a couple games where a few asshats would leave everyone they played with negative rep. I got stuck in two games like that where almost 70 percent of the people playing in the big team battle match were friends and one of them would say. "hey guys leave so and so negative rep tehheee tra la la". Two times in a row that "so and so" was me. :(

Eventually I did come back and it has been fun hence forth.