This is one of those clever marketing wheezes. They know that only a small proportion of the guarantees issued will ever be acted upon, so the financial liability will be very limited. But in the showroom, it's doubtless a fairly powerful selling point. I had a few lifetime warranties on exhaust systems but unless you keep the receipt handy until it fails (and remember that you have it), it's of no value. And similarly, when the vehicle is sold on, that continuity is almost invariably lost.
The other classic con is the gift card. You can only spend them in "their" stores, they often have an expiry date and if you misplace or lose them, the entire value is lost. They can't lose. I'd love to see the final numbers but I'd suspect they only end up reimbursing 60-70% of the face value in many cases.
You also have to think about what is meant by a "guarantee". It may be reasonably clear in the OP example but often it simply means that if the product fails they will replace it. For me a classic example was the Armadillo "guaranteed puncture proof" Kevlar-lined tyre for my bike that developed a puncture after 1 mile, literally – I ran over a small bramble on the road on the way back from the pub that first evening after changing both tyres. The jobsworth at the other end of the phone said I could have another one if I sent the "old"(??) one back. What a fantastic offer.
Murray