Very rare indeed as walnut is always scrutinized for the possibility of selling to the veneer market. That is really the place where all rare really...
A lot of people put too much pressure down on the sander and that prematurely causes velcro wear. The heat generated doesn't help. 5 years is really...
The part you are forgetting in the equation is the tensile strength of the material. Grey iron tensile strength is quite low. In metric, the ultimate...
I'm a big fan on old iron for a thickness planer. Back in the day I bought a 24" Yates American machine. You could take 1/4" cuts on 12" wide boards...
Paul describes it perfectly. The trimmer tools are just fine for plastic edge banding, horrible on wood. I also follow up the iron with a wood block...