Must be said I generally work on 150dpi for any image over A3 size - generally something this big is likely to be viewed at a distance so you can drop the dpi. A3 and below I use 300dpi, sometimes 600 for a photo size image to wallmount.

I agree with Davids starting point on the thread, you can't get to a big enough res without using render to disc and this means you're at the whim of any system failure that comes along, although for big images I will go to the bother of setting up network rendering to quicken the pace. IMHO I'd be fine to use render to disc if there was a way of re-starting after a failure, DAZ could easily hide some reference information in the image file to note how far the image has gone along, or create a second render progress file....

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Toolset: Blender, GIMP, Indigo Render, LuxRender, TopMod, Knotplot, Ivy Gen, Plant Studio.