I noticed that the inside of the rear tires, wear much quicker then the middle to outside edge.
I have only put on 6000 km this summer on a set of new rears and the inside edge is 2 mm from the wear bar, the middle to outer edge looks like new.

Is this normal or should I get an alignment or something?

 

It's normal due to the negative camber.

Depending on your driving, rears should last about 10k miles. Fronts twice as long.

 

like you jumper...i have a c4s with 19's...the conti's in the rear barely got 7k miles...told it was normal

 

Try lowering tire pressure a little esp during summer as rears heat up and expand air inside tire a lot. 40psi is usually good enough.

 

can corner like hell on two wheels. don't waste good rubber.

 

try unmounting and remounting the tires on the other side at 3-5K on the next set, should get them to last a little longer, but it sure is a common prob...