It certainly helps if your negatives are similar in density and contrast, makes the guestimation much more accurate.
When I want multiple prints of the same negative, I just work until I get the final print that I want, then expose the paper for the rest of the prints all at once and run them through the chemistry 2 at a time.
... All I'm saying is, I think my best prints (probably 'bout 5-6% of total) are pretty dang nice and I just can't see what I could have done to make them any better by putting more time into them.
I learned this from John Sexton:
Take those prints and hang them temporarily in your house at a place where you walk by all the time. Let them sink in for a few days maybe weeks. The improvement opportunities will become obvious. If not, maybe they are perfect!