Game freezes after about 15 min of play.

I get also freezes after 2-5 minutes after loading a save. But this lasts "only" for ~20-30 seconds, and from that on it runs smooth. 

How long did you wait?

I had a similar issue. Try reinstalling the game?

I've had a similar problem. I've played about 30 minutes and the game started to really slow down. Had to save and quit because it was progressing.