No, not in the US. It can't be - American consumer product law prohibits them from enforcing it.
> do they make you produce the original invoice during that period?
Yes, they do. They make you provide the original invoice very often even if you did register with the card.
> It feels like they don't want to honor 5 year coverage and so set you up to fail.
That is my perception too. I am hyper-sensitive about this sort of thing and I have all of my receipts going back more than ten years, both the originals and digital scans of them. I have on more than one occasion had to send them a copy of the invoice a second time - this has happened at LEAST three times, in fact. (I have more equipment than most folks, and I probably also shoot more than many amateurs too. It's not that it's particularly unreliable.) I definitely have the sense that I'm guilty of trying to get something out of them to which I'm not entitled until I prove that I'm legit.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!