you'd be surprised. ive ran -3 on my past cars and still get 30k+ miles on a set of tires. at -3 in the rear, i go through a set of rear tires within 10k miles. toe is at .05 as recommended by a lot of other forum members to correct tire wear
i have those adjustable rear camber bushing and do not recommend getting them as they dont provide enough adjustment. i was only able to go from -3 to -2. i would recommend getting rear adjustable camber arms made or wait for mountain pass to make the model S ones.
i dont have enough data at -2 yet to give any real results but ideally i want to pull it back to -1