I drive a 996 carbrio. Purchased it last year and immediately put new tires on. 225/40 18's in front and 285/40 18's on the back. Michelin Pilot Sport 4S's.
I've put ~ 25,000 miles on the car this year and the rears are already due to be replaced. After the fact, I read,

"30,000 Miles warranty - Half mileage for rear if different size than front"

I have 2 questions:
1) What rear tire would be a good recommendation that does not need to be replaced every 20,000 miles? I don't drive crazy, just a lot. No track days, just street driving.

2) alignment - I feel like the car drifts in the back, rides in the ruts of the road a bit. I had the car aligned when I put the new tires on, and like all porsches the insides of the rear tires are wearing slightly faster than the outside.
Does anyone have other alignment specs that help the car to not feel so tail happy in bad weather?