On my Kindle Kbd 3rd Gen WiFi I requested a replacement after just one week since it kept shorting out. The replacement also shorted on an intermittent basis.
I kept it for 3 month and just tolerated the intermittant shorts until I realized it was the unlighted cover with the two metal hooks shorting the Kindle. I posted that thread here and dozens confirmed the same situation as me.
Then I called Amazon CS and directed them to the thread here. They reviewed it and gave me full cash back on the cover even though it was well past the 30 day refund period.
I rarely return purchases from Amazon unless they are DOA when I open the box. If they turn defective months later, I just discard them and eat the loss. That happens very rarely.