A significant percentage of valve seat failures are due to wrong parts or incorrect valvetrain geometry.
Why are there so many grinding stones? Because each has different characteristics and uses.
For an ultra-smooth surface finish, know the metallurgy of the castings and the head gasket.
Cylinder liners or sleeves continue to be the saving grace for new aluminum and vintage iron blocks.
The key to honing is to get the rings to seal against the cylinder wall by making just enough valley depth.