When does seller's responsibility end?


I'm sure this has been discussed before, but a search could not find it.
I sold a Naim DAC (mentioning this because Naim is notoriously reliable) to someone on November 26, shipped on November 27, 2012.
Did not hear anything one way or another until December 19, when seller emailed to say one USB input would not work with his ipod. Well the input worked for me when I had it. I asked him to be sure he was doing everything correctly, including checking for bad cable. I am not sure the input really does not work.
No word again until December 25, when he asked if I would pay for repair. I answered no, because I felt the time period had been too long and my responsibility was over.
Now he has initiated a dispute/claim against me on Paypal. They have put my account in the negative for the amount of DAC until they resolve it.
Sorry for the long post, I just wonder if there is a consensus on how long a seller should be responsible for "sold" gear. I say a week, maximum.
What say ye?
Ag insider logo xs@2xmuzikat
Thanks to all.
Sgordon1 that is exactly the problem. Nothing has been diagnosed, nor has any cost of repair been put forth. It is all based on his word to Paypal.
I believe if the USB isn't working it is due to user error.
This might be an individual decision, after a month, I would take care of my customer and pay for repairs. A situation similar to yours happened to me several years ago. I ended up loosing a few hundred dollars but suffered no heart ache and the buyer was very happy.
To validate the buyer's argument, why not ask the buyer to send you his Ipod so you can check it out for yourself... ... ... fair is fair.
I would take the DAC back, with the buyer paying the return shipping, and refund his payment less any costs incurred for ebay and paypal.

You can resell it. I would indicate no returns in my next ad.
IMO as soon as item is delivered and confirmed to be in working order. I would say 24-48 hours or so after delivered.