I've never bought anything that had an EPA sticker on it and my newest car was 10 years old when I bought it. Wait, I take that back, when my dad got a new car and I got his old one that one was I think 6 or 7 years old. But I also researched the cars I've purchased and knew what kind of mileage I should expect from them. The one that did surprise me was my motorcycle. I wasn't expecting the mileage to be so good on that one lol.
The thing about those stickers is that those numbers are from controlled tests. There are no hills, stop and go, heavy acceleration etc. etc... If you get even close you are doing good.