I've had renders over 11 days per frame, as Aldaron said, to renderfarm you can use Bryce Lightning for each of the farm machines, no need to buy extra licensed versions of bryce, you only need your single licensed client. Ditto with using single images, means you can also do tricks like batch processing photoshop filters on the image set etc...

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