I guess the bottom line really is this:  how do you achieve those neat real-light effects in a useful and practical way.  A 90 hour render is obviously not a pleasant option no matter what the final result is.  One of my full size renders using that "volumetric world" option, for example, would take about a thousand hours to complete, so I never use it.

Now I have to go and figure out how to successfully use HDRI on an indoor scene, with ceilings and all.

"An Example is worth Ten Thousand Words"