You need to change your mentality man. Old games lose value to 0, and you aren't likely playing them much.
Why the hell waste that opportunity to save some money?
Buy games the day the come out if you want them, once you know you're done with it, get the fuck rid of it. Especially sports games, if you have lost the fun after 5-6 months, then don't hang on to it, once the season in real life ends that game will drop to like 15 bucks credit. Before the season ends it'll be 30-40.
I'm on a never ending cycle of buying games for half off or less, just by recycling games that I've beat 3 times over and don't want to keep.
Collect things that go up in value, get rid of things that lose value. Saving Money 101.