Not sure I have ever seen your roof up Will, so perhaps that accounts for the lack of wear
More seriously, I too doubt the 'value' of these extended warranties. I believe you would be best off to ensure the dealer records on your car records your concerns prior to warranty expiry and from what we have seen a "goodwill gesture" (up to a limit - I think it is 6 years from first registration) may be more fruitful.
Sad to hear though of repeated problems but seems Nissan did not learn enough lessons from similar issues with the 350 roadsters - as martinmac can testify.