Originally Posted by Scholar
I used to do this, too. The last game I traded in was Sleeping Dogs, and I really regretted it, so when PSN offered it as a free download for subscribers, I went for it again.
Some games are definitely not worth a 2nd play through, but I give a few of them a play through or just pick up where I left off just to see if I can edge closer to 100%. I never have done it for any game, though.
Before my '360 broke down for the third time and i switched to PS3, I had a larger library of games I was holding onto for a second/third play-through...... Red Dead, Arkham City, GTA, Fallout, New Vegas.... but I traded them all in towards a new console.
I don't do online multiplayer outside of the occasional 2k13 game, and with all the new games coming out I don't really have time to go back and play old games again as well as the new ones. So keeping them around isn't worth it when I can get $10-$20 off the new games.
I'm just finishing Tomb Raider, and will likely trade it in just in time to get some money off The Last of Us.