I found a pristine steak knife some time ago, now like 10 burlap strips, a deer and many cans later it is still pristine, so it might not wear off at all.
i'll keep an eye on that
edit:
now another 20 cans and some strips later it has turned worn
so it seems like it is, afiar, wearing off much slower then other knifes
if this mechanic changed for all knifes, forget about this, but since a steak knife seems a bit more fragile then others, this might need some tweaking