Maybe this is common knowledge and I just figured it out, or maybe I discovered something! I've been using 3" rolocs for grinding and have noticed that they typically wear out on the outer diameter but still have lots of grit left towards the center. Aha! I take the worn out 3" ones and mount them on a 2" mandrel and use a not so great pair of snips to cut around the circumference. I then have a new working surface and have doubled their life.
Anybody else do this?