I would expect the game to be less than optimized at this point since it's Early Access. One work around to a possible memory leak is the exit / restart the game before you start experiencing the lagging. I don't play this game, but I do play Fishing Planet (awesome by the way if you like fishing in real life) and it has a similar issue. At about the three hour mark or so, my frame rate drops when I am casting or have my line in the water. As long as I'm not attempting to cast and my line is in, my frame rate stays at a constant 60fps. Beyond the frame rate, there is a huge input lag, so if I turn, it doesn't respond immediately and then all of a sudden it catches up. The odd thing is, Rust and Fishing Planet both use the Unity 3D...