Set up a scene yesterday, set it to render overnight as I expected it to take a few hours. Got up this morning, still rendering. Finally finished after 11 hours and 55 minutes.

The main culprit was a hair figure (Goya Hair for M4). Rendering that in a scene with IDL, multiple lights and 3 bounces took forever. I rendered the scene (from a different angle, where the hair occupied less 'real estate' on the image) and made the hair invisible. Rendered again, took just under 2 hours.

Tried then doing an area render of the hair with reduced settings, but after an hour had barely done 100 pixels in the precalc indirect lighting pass, so...

cancelled the area render, went to D3D's firefly render settings, changed to progressive render, set samples to 12, then used area render again. Half an hour later, it's done. The artifacts are invisible because of the type of hair figure it is... basically the thing that caused problems for IDL are what let me get away with this using progressive. Had I done this for the previous scene, I'd have saved myself roughly 5 or 6 hours. I still have to merge the 2 images, but that is literally 2 minutes with the eraser tool...

Might come in handy for someone...