Apple stores not consistent
I set out this week to get my bumper replaced because, like so many on here, the rubber at the bottom of the bumper, near the home button, had come loose.
On Thursday, after reading the posts here, I tried to exchange it at the Polaris Apple Store (Columbus, Ohio). The employee looked at it, heard my request and then went into the back room "to check on something". He came out and told me that they weren't covered under a warranty. He told me he had talked with a genius and "wear" wasn't covered. I tried to tell him that it was obviously a problem if it wore out before the phone did. I mentioned to him that others had exchanged theirs and that there was even a code for it. He said there wasn't... he had checked.
Yesterday I went to the Easton (Columbus, Ohio) store and told the employee that I had "defective" bumper. (Magic words?) She said, "No problem, we can replace it." She set up a genius appointment for me (later I was told that this wasn't needed.) The Genius looked at it, said, "No problem" but wouldn't let me change colors.
My advise: The warranty covers defects. In my opinion a case that lasts less than a year is defective. Use that language. Clearly ask for an exchange. Good luck!