After about an hour or so my framerate drops drastically from a steady 120 to 64 and sometimes lower. I've tested it numerous times at the exact same locations, exact same saves; as soon as the game started chugging I saved, quit the game, restarted it and voila -- flawless victory.

Anyone else suffering from this? If not I might have to take a good hard look at my rig.. Troubleshooting, yay.