I very seldom fill out "warranty" registrations on anything. In most states, they cannot deny warranty for not filling "warranty" registrations. Check your local laws and regulations.
It is 99.9% about collecting customer info for marketing purposes, and 0.01% about warranty. Have a friend who works in the advertising business and he says to not fill out warranty cards if you don't feel like it. Ever notice how, for some things, that filling out warranty cards makes you eligible for "prizes and "special" offers.
Another friend who works in the security world says to NEVER fill them out.
Save your receipts, that is worth way more than a filled out warranty registration.