Your replies put me to shame. I clean and lubricate everything regularly and only change a chain or cassette when I notice problems with running or shifting. But I ride mtbs and not with the latest top-end derailleurs so perhaps I'd do differently then.

At the UK Bike Show recently they showed the bike that Kulhavy won the cross-country at the Olympics on. The chain and cassette were absolutely knackered after just one race of about 35km which goes to show that it depends totally on the type of riding.