It may depend on when you are renting and the company you are using. When I rented an SUV in mid-January this year, I reserved it in December. There weren't any great deals. Some of the phone agents looked through the discount codes & found that there were none in the system past a certain date. Maybe because it was the end of the year? The Hertz person was nice enough to say that this did not mean rates were really high, but rather that they just hadn't released the discounts yet. Sure enough, I checked back a little before the others expired & got a great rate with a new promotion!