I almost never go over 10% quality or density on Volumetrics. I'm too darn impatient to wait that long for any image. Especially when I am starting to re-render them for printing posters. I also make sure I use the most aggressive optomization and set it (most times) for clustered scenes. If I use plop render, I plop out the easy sections first. Makes me feel like I've done something. And then I whittle away at the edges of the hard stuff (clouds, lights, etc.) till it can chew them pretty fast. I hear your pain Gog... been there, done that, have the tee-shirt, want to see the slides? :c)