The GP4000s is a performance tyre rather than an endurance tyre. If you imagine running across broken glass as en extreme example, then the GP4000's will suffer more damage than something like the Gatorskin, and subsequently they are more prone to punctures.
Like I said they GP4000s is a great tyre, but just don't expect them to last like the endurance versions.
As for mileage that depends on too many factors. My tyres never last anyway due to the condition of the roads around here, so even if someone told me a tyre would last 5000 miles, under my ownership I know full well that it wouldn't.
I go for puncture protection first and foremost these days, and touch would Gatorskins have never let me down