No amount of dust, grime or grit on an LP is going to wear down a diamond needle, no matter how long you use it. As a previous commenter noted, diamonds are cut using other diamonds because nothing else will work.
The Hardest Naturally Occurring Substance on Earth
Yep - You all know from grammar school that is the diamond, which incidentally is what is used to make the stylus of our turntable cartridges. If it is so hard, and it is going up against some fairly soft vinyl, why do we worry about poor quality LPs damaging the cartridge or stylus? Sure, I understand the cantilever, but the actual Stylus? The old phrase for me is "Does Not Compute". What are your thoughts and insights?