I never ever get rid of them, I have friend who keeps trading in games so frequently that you can never guarentee that he'll have them when you come over. It's like:
"I'll trade in Tenchu Z for COD:WAW."
"I want Tenchu back, I shall now trade in Halo 3."
"I will trade my copy of Soul Calibur 4 to get my copy of Halo 3 back."
"I want Gears of War 2, so I'll trade in COD:WAW Halo 3 and Tenchu Z to get it."
"I will now trade Gears 2 for Rock Band."
"I will trade Rock Band for L4D."
"I'm off to go trade L4D for a store discount."
"Hey... where did all my games go?"
He just keeps doing this, getting rid of his games then wanting them back and deciding to get rid of another game to do so. He is the absolute worst shopper on the planet because the way he does things and the rate of how fast he does it means he is essentially paying $70 dollars FOR A RENTAL. If he's going to take such a wierd approach why not just rent the games and save seven hundred dollars?
I keep every game I choose out because I like knowing that I have them and can always rely on that in case of a rainy day. That's being LOGICAL.
..besides I don't need to trade, I've got money pouring out the wazzo so (*blows a big fat raspberry*) to that.