Interesting to see other's experiences with chain/cassette wear. I too have a chain-wear tool, and change the chain at 0.5% wear, usually after 3 to 4,000 miles, depending on weather and riding conditions. My cassette is currently on it's fifth chain (SRAM PC1110, Ultegra cassette) and no sign of any skipping...
I always give the chain a good wipe-down after every ride, to get as much grit off as possible.