There's no straightforward answer to this. My previous regular commute had a Campy 9-speed groupset and I found that the chain lasted me about 10,000 miles. My new commute came with SRAM Force 11 groupset but the cheapskate manufacturers put on bottom of the range PC 1110 chain and cassette. That chain only lasted 2,000 miles. I replaced with the 1170 chain which has so far done another 2,000 miles with no sign of wear. I've never had to replace a cassette because of wear.