I get 10's of thousands of miles on 9 speed Shimano cassettes (closing in on 30,000 with current 9 speed XT cassette). We should all acknowledge that wear on the different cogs can be hugely different. It depends if you typically use just 1 or 2 cogs and which cogs you typically use. For instance, a 14T cog will wear twice as fast as a 28T cog. Then, if you ride in that 14T cog for 80% of the time, well then yea, that cog will wear out fairly quickly while the rest of the cassette is in near new condition. So someone that rides in a small cog most of the time may get only 3,000 miles, while someone that rides a lot of rolling terrain, and thus uses a lot of different cogs including the larger ones can get 30,000+ miles.


I personally use the middle cogs (16//18/21/24) most but I also do climbs and use my largest cogs (28/32) a fair amount. The smallest 3 cogs get used the least. For those that change their cassettes before 10,000 miles, I would be interested in knowing what they are basing their decision on. Noise, bad shifting, chain skipping under load, visual, anecdotal stories told to them by their riding buddies, advice from strangers on forums, or just following what the pros (who don't pay for their gear) do?


Also, why are people so existed about the new Shimano and SRAM cassettes with 10T cogs. Lower weight (including in your wallet)?