Here's the lolipop question...how many razors to the bottom of a Naniwa stone?

After honing a number of wedges in particular, I've noticed a moderate amount of wear on my Naniwa stones and I'm concerned that I'm only going to get a couple hundred antique store finds honed before these guys look like 100# paper. I imagine if all I were doing was touching up razors, these things would last for a generation, but antique store finds are killing my hones!

So the question is, has anyone had noticable wear and tear on their Naniwas?