i live in manhattan. for manhattan residents, avis has its "rent control" program. for every eight or so rentals, i get a free rental day.

i am also an avis preferred select member. i don't think they give me free rental days for a certain number of rentals. but, they have coupons on preferredselect.com giving a free day on three day rentals. the coupons are re-useable.

in my opinion, however, the preferred select program is pretty worthless.