All of us happened to be in that situation: full cgi scene in Blender, gorgeous lighting, loads of objects in the scene, aaand render times take forever.
For 1 single frame.
Especially when it comes to volumetric lights (to which Im addicted), the so called godrays, render times go crazy.
Here is an alternative quick solution that cuts drasticly your render times and give you gorgeous renders with volumetric lights at the same time!