I send mine in so help them with the demographic info that it contains. And for the Recall info, just in case. Plus you never know down the road if the policy might change regarding the Lifetime Warranty.
The last Taurus I bought did not have a warranty card, so I called to ask about it. Customer service told me I don't need one, and they are discontinuing the cards since they have a lifetime warranty. Just send it in with the repair form available on line at their website. Doesn't matter if you're the first or fifth owner.