It depends on several factors.
1. Do you keep your tires properly inflated?
2. Do you keep your car properly alligned?
3. Do you keep them balanced?
Since Boxter tires are unidirectional and two different sizes, short of dismounting them and swapping rims for the fronts and rears, you really cannot rotate them. So allignment and inflation are the two biggest causes of premature wear patterns.
Your driving patterns also affect wear. If you spend a lot of time trying to get maximum g's in your turns, you will get more wear.
The roads you drive on also affect wear. Smoothness of the asphault/concrete/pavement will affect wear.
I got 35,000 miles out of the original Conti's on my boxster. They could have gone probably 5,000 more, but I got a fantastic deal on some P-zero's.....
