Haven't seen many around here as they don't typically have sports cars for rent due to the weather. You can only really drive them 8 months of the year.
I can tell you that I rented a 1SS A8 car in southern California for a week back in the late part of 2016. That car had 2800 miles on it when they handed me the keys. It had 3100 on it when I handed them back they keys. I noticed that it had mismatched tires on the rear when I picked it up so it had already gone through a set in the first 2800 miles of it's life. The 2nd set were down past the wear indicators when I dropped it off and I felt the need to take it to a spray was to get all the rubber off the fenders and wheel wells.
Moral of the story is don't buy a rental. I don't care how good the warranty is. I've literally seen air time in rentals on back roads.