* I'd probably replace the 'alpine fractal' node in the terrain tab with a regular power fractal terrain. I have noticed an immense speed increase by doing this for other variations on this scene. I'd figured that since there isn't much visible mountains in the scene and that they are blended way into the distance, that an alpine wouldn't add too much unnecessary render time. It does.
A few render buckets have areas of terrain that really hang for ages with the silly alpine I've left in, so, I simply added a new power fractal terrain and replaced it to the position and blending of the existing alpine. A few lucky-seed clicks, if required, should give you much friendlier results. The BG mountains were really just filler, anyway. Although, it's up to you.
Got another HQ test scene cooking using this file just now and it's much faster since replacing the above.
