I got about 5,000 miles out of my last chain, a 105. I'd measure it periodically with a ruler, and it barely showed any wear and ran fine. I bought a new crank and put the old chain on it, thinking it was still good, and it ran like crap. Put a new chain on and it now runs good. So, I don't know. I think 3K miles is about right for me. I do ride in the winter, which around here means lots of grit and salt, but I am a little obsessive about running a clean drivetrain.