Manufacturer warranties usually apply only to products that are sold by authorized retailers. They often mean nothing at all on eBay. eBay also has no interest in policing quality of warranty service by sellers. If you have a problem 90 days after buying something, you're at the mercy of the seller, because there is absolutely nothing you can do about it on eBay once you've paid and left feedback.
That is why most sellers will kiss your butt until the point at which your feedback and resolution center actions can have no adverse effect on them, and then forget you exist.