I have a relatively high rate of returns because I am taking previously published stories, repackaging them, and publishing them under my own imprint.
And although I try to clearly mark every one as PREVIOUSLY PUBLISHED I still get a few -- almost instant -- returns. So it's someone who saw the new cover, thought it was a new book, and realized their mistake too late. To our mutual disappointment.
I don't think it's necessarily wrong to take returns (though I'm pleased B&N and most of my other publishers won't accept them) but seven days does seem exorbitant.
If I buy something online and make a mistake and ask for a refund, it is within minutes. I think Amazon should have a "no refund" policy after ten minutes of purchase....but we know ....the customer is always right...LOL