Is Apple only allowed to exchange out of the box defects once?
My family went in for iPhone upgrades today (all went from the iPhone 4 to the 5). I had heard about the scratches and nicks fresh out of the box, so I made sure that everyone's iPhones looked good. Mine had a huge scratch on the back, and they said they would exchange it but that they could only do it once. So they did and my new one had no scratches or any issues. My mother's iPhone, however, had a distorted volume button that stuck out (even worse than my scratch on the back). So she told the apple worker and he said he'd bring a new one but that he could only do it once and after they couldn't bring another (same thing they told me). However, when she got her new phone, it had three big scratches along the antenna band. She noticed them but said she would just not say anything since they said they'd only exchange them once. I told her that it wouldn't hurt her to ask, and she did but they said they couldn't do it anymore. She said it didn't bother her, but I thought it was odd how they could only exchange it once - even if the second phone she receives also has clear defects out of the box.
So is Apple only allowed to exchange out of the box defects once? My mother said it doesn't bug her but for the amount that she paid I assume she was expecting a high quality product with no defects or out of the box scratches. She just bought hers today. Should my mother have done or said something about it? Is this normal for Apple to only exchange defected iPhones once?