I got 4,800 km out of Metz, 6,500 out of Avon Cobra and 10,000 km from Exedra Max. I would attribute some the improvement with the Exedra to the higher profile because,as I noted elsewhere, the slightly taller gearing makes it a little less likely to break away on hard acceleration - you know, those inadvertent wheel spins that help rip up the tyres. But they also seem to be inherently harder wearing. They're also flatter than the othe 2 so I'm if find they wear far more evenly across the full width and less down the middle.
Zen, if you don't like it don't use it but i can assure you that as far as I'm concerned the improvement is real and noticeable.