Same here - I have yet to decide I don't like a game, trade it in and change my mind. And I trade in a LOT of games.
If I liked a game, finished it, and have good memories of it, I'll keep it "just in case".
Its just the games that just give me a feeling of "well, this is the only playthrough I'll do EVER" or even "I hate this, I am bored, not entertained" that I trade in. I am picky though so I try a lot of trade back a lot too. :)