I asked three different employees, including a manager, about my local Sam's Club return policy. They all stated that I could return the item at any time as long as I had the receipt.
I asked what the time limit was, 30 days, 60, 90, six months? All responded, "as long as you have the receipt" and it doesn't have obvious signs of abuse (cracked screen, etc.). No time limit. They showed me the sign posted in the store stating these facts.
Which is why I keep mine in a case. When the battery dies, I'm taking it back for a new one.