The tire warranty from the dealer I'm referring to was for any runflat tire for the duration of the new car warranty. So you could swap out the original tires and the new set would still be covered. Tires don't generally last 4 years / 50k miles for me, so for my driving habits it would have covered at least 2 sets.

And it would replace a damaged tire, not patch it.

I'm not trying to sell it to anyone - I didn't buy it myself. I'm just relaying what I was offered and why it would have been tempting if I was planning on sticking with runflats.