Andy's estimate is spot on for me. The trick is what your workflow is. I prefer to print a work print (right contrast and exposure, maybe some obvious burn and dodge) and live with it for a while.....put it in my office, darkroom or some other place I see it regularly. Then I decide how I want to print it as a final print, I do that probably at a larger size. You are much better to put out 4 amazing prints per year than 40 OK prints so don't feel any time pressure. If you don't have enough time in one session, that is OK.