I recently started taking a class by Jason Martin through GameartInstitute. One of our early assignments was to make some head sculpts and then take one of them a bit further by blocking out the body. Time spent on the heads averages from 1hr to 6hrs.
I really wanted to to do something that was eyeless with split jaw. So I decided on this concept and have spent about 18hrs so far blocking. Everything is pretty loose at the moment