... watch manufacturer, should Panerai investigate this matter and find that there is a technical flaw in the design of the product that may or may not materialize for some watches, they will either extend warranty or adjust the manufacturing process, create a flawless case and then replace cases....
I would not worry about it too much for now. In addition, at least that is the case where I live, what most consumers do not realize that most of the times they have more warranty than the warranty period given by the manufacturer. Clearly, this does not apply to normal wear and tear etc .
But in this case, ie a very expensive watch, one could expect that the product purchased is free of inherent flaws/technical errors etc. So if the manufacturer provides a 2 year warranty, but say that after 3 years it becomes apparent that there is a serious problem with the case, enitrely because of the way it was constructed / designed, and of which one could expect that for the price of such an expensive watch, there would not be such flaws in the product, then I would be reasonably confident that you could still hold them to the guarantee....