I would always clean when I sharpen....harder use....more cleans and more need to touch up the edge. It depends on how the blade is used as well. If I used it for meat/food I would remove the tannin marks and sap stains....no use being proud and stuck on the toilet! But I agree....a used look has a much more professional image for the knife...they say you can tell a lot about anyone by their kit when they are outdoors....some people look like it is home...some people look like they just walked out of a shop!

Several miles down the road and they often need a taxi....

I always say you treat your guns and knives like you treat your boots. Well used, comfortable and looked after.....