I recently began to use my Fat Boy on 9 for my first pass after a four day growth as it mows down the overgrown "lawn" much more efficiently. Subsequent passes were at 5.
Today's shave, after four days of growth, felt a bit different. The razor seemed to have more bite to it and my skin felt a bit more sensitive as the shaved progressed. But, I just went with it since I needed to wrap it up and get to work.
During cleanup of the razor I made a small discovery. I forgot to dial it down to 5 from 9 for pass two, three and four. So all four passes were at 9 using a G7OC that already had 8 shaves on it. Wow, I never thought I'd be able to run 4 passes on 9 with my Fat Boy.
Moral of the story...ignorance is bliss. You can do "great" things if you aren't aware that you're doing them at the moment.
Oops!