That's just trait of this Mk2 chassis, pushes the tyres into the road so well they wear out faster it would seem.
Don't do a great deal of mileage myself, but I've had the Vredestein's on for around 9 months and they are wearing well. But the fronts are certainly wearing much faster than the rears, might have to swap front to back soon to even it out. I reckon 10,000 miles is probably a good estimate really for most performance tyres on the Mk2.