For me it vastly depends on the amount of details there is on a model.
Example: Saurus Guard vs. Skinks.
I can paint a unit of 20 Skinks in two to four evenings I think, which is 12 hours or so. Working on the same quality for Saurus Guard takes two weeks, so around 50 hours, just becasue those have four times as many details to paint.
EDIT: Saurus Warriors are somewhere in between. I guess maybe 30 hours or so for 10.