It depends on the shadows, hair, shaders, etc. but these were rendered in Daz Studio so they only took a few minutes. The ship's bridge (pages 7 and on) were rendered in 3DS Max so they took a little longer. Later on there are some that took about an hour or so with all the shadows turned on.
The only ones that took that long were in the mansion on page 41 because of all the deep shadows. Some of the caves took about 30 mins but most everything took less than 10 - 15 mins.
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