Pat
Do they get dull? Don't know. Actually, the finish I use doesn't get super shiney. Instead, it's sort of a soft gloss.
I have three 'pens' that are in my 'daily carry' selection - actually, two fountain pens and one stylus. One fountain pen has a CA finish, the other has a waterborne poly finish, and the styus has a friction polish finish. After several years of use, I can't say that any of them have changed significantly. One thing to keep in mind is that some timbers are softer, and as time goes by, the timber itself will pick up dings and scratches. To me, that's part of the natural aging process. If I wanted them to look pristine, I would put them in a box on the shelf and never use them.
We had a guy here in the US who manufactured specialty photographic equipment. One of his products was a very high-quality wooden tripod that I think he made from ash. When people criticized his tripod because it could get dinged, his response that wood is like people - as it ages, it gets honorable scars'.