I know they don't wear down easily. I've had mine for almost 3 years. The arena footing was recently changed, so it's rubber on top of dirt footing. The two mixed together create a "gummy" sort of mixture. I can scrape the stuff off of my stirrups, but I was just wondering if a fresh set of cheese grater pads might make this issue a little less obvious. The "gummy" stuff makes my feet slide around a lot.
We have woodchips for footing in our indoor and I have the same problem all winter. The footing gets built up on my cheese graters and I slip out of them. I replaced them and it didn't help. Just have to clean them all the time, I found a wire-bristled brush works like a charm!
I've had mine for 7 years and I bought them used from a friend. Mine do the same thing and i just grab a hoof pick (which is always by our mounting block) and run it one or two times through the rows and it falls out in clumps.