You even have some of the tricks in default Blender. For example for interior scenes you use Simplify menu in render tab, and limit AO bounces to 1 (or 2, but the cut in render time will be less than with 1). Then in World tab you enable Ambient Occlusion and set appropriately the values there for your particular case. This could cut render time in half in some scenes.
The point is, these things should never be by default because ideally it would not limit too much bounces, nor Clamp too much lights, nor any other trick that can make the results unstable especially for animation (although these tricks can be useful in some cases)
For Scrambling Distance you can search here for BoneMaster or BoneStudio builds: