I've reduced my render times by making all my lights ranged instead of linear. I usually have around 30 lights in a scene, but because I use them just to light the bits I want it doesn't really increase render time. For stuff with volumetrics in the background, this can speed up renders by - I reckon - at least 20X. I now used the saved time to render big (3K x 3K) on "default", or sometimes even just "preview", which when reduced for the web gives a better smoothing than 9 pixels "superfine" on, say, 800 x 800.