In my experience with the Curtis skids, they don't wear out but break off at the weld. I ash canned them years ago and went to the Moose 5/8" replacement skids from Dennis Kirk. They are thicker bottoms and the shaft is threaded into the skid before welding. I haven't had one break off in a couple years.
The downside is you will probably have to increase the mounting holes from 1/2" to 5/8" but a small price to pay for the improved skids.
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