A while ago, I assembled a nice set of Freud Forstner bits. They work well, and lately I've been using the 7/8", 1-1/16", 1-1/2" and 1-3/4" sizes while making pepper mills. The pepper mill holes include deep drilling in endgrain and I can now tell that these sizes are becoming disproportionately dull compared to the rest of the set. I'm considering getting those four sizes and dedicating them for mill use. What are my best choices given the task at hand? Should I be considering carbide?