Fps drops more and more the longer the game goes on

Start off the game with about 250fps on ultra, 5 minutes in my frames are down to about 120, about 20 minutes in they are down to 60, 30 minutes in they stay at around 30-40 fps for the rest of the game. Doesn't matter if i lower the graphics quality. Holding space to lock the camera on my character seems to cause significant frame drops at times, other times it doesn't. What the heck is going on here, this didn't happen in the pbe build...