I was the first to answer, but I also change my chain and sprockets in sets. I never put a new chain on a used sprocket. May last rear sprocket showed no visible wear and the front only slight wear and I still changed all 3 as a set. I have old set hanging on the shed wall as I think it had a little life left in it. If memory serves I got about 23,000 out of it with no lube but I forget for sure, I know it was over 20,000.
