Rick,
LV also offers sharpening cones for these punches, I suggest you secure these as well. Like Splint mentioned, these punches are really bits for a mortising machine but with handles. I have a mortise machine and I've experienced the dulling of the square bits, especially after a larger cabinet like build with many mortises. Then they start to become hard to use, and sometimes cause dulled and rounded entry edges on the mortise due to breaking grain rather than cutting the wood.