I was talking to my tyre man yesterday when I took my original wheels in for a set of new "summer" tyres, ready for spring.
He was telling me that he has one customer with a A6 3.0 Quattro who would get through a set of "summer" tyres in 12,000 miles. A few years ago he fitted a set of winters at this time of year and left them on through all of the next year. He got 24,000 miles out of them, so now runs them all year round.