joelmoskowitz
It's in the literature. If you actually use a plane to dress wood you will ear it out and what was done is the newest planes were used for final jointing and smoothing, as they wore they were demoted to lesser tasks. I will look it might be in Joiner and Cabinetmaker but I might be wrong.

BTW if you are wondering why it is pretty easy to find late 18th century molding and special planes but late 18th century wooden smooth planes are very rare - it's because the most used planes wore out.