Before you get excited: I haven't rendered an animation, yet.
However, while I was working on optimizing render settings of the alpine pack for an animation, I was able to realize a 64% speed improvement for a Full HD render of the alpine pack.
Of course it had to be realized by reducing quality, but my intent was to reach maximum savings without a quality sacrifice that would be noteable *in an animation*.
The first image rendered in 16 minutes, the second image (with settings optimized for a still) rendered in 47 minutes.
THIS MEANS the optimized pack was 3 times faster! I reckon that's pretty significant.
You will notice a difference in the colors, which is partly due to the fill light setup of the faster render, which hasn't been adjusted to meet the ambient light requirements of this scene (too much blue, not enough red).
Anyway, I thought you might be interested in the comparison. Here we go....