I purchased a Samsung S4 April 2015 and started having issues with the power button. I called the company and was on hold for a few minutes before talking with someone. Michael asked me for my order information and luckily, I purchased the extended warranty. He provided a prepaid label and a week later, I had a new S4 in my hands.
Since these are used devices, buy the 1 year warranty. Failure to protect yourself it your own fault. 4/5 as the phone did not last an entire year but they resolved my issues. Will buy again.