Here's the catch tho...I decided AGAINST the tire certificates for the following reason. After 10k miles, with all tires significantly worn, if I have an unrepairable tire, the Certificate pays for the replacement, but does NOT pay for the replacement on the same axle. In this scenario, the cost of the certificates isn't justified.
Before I got certs, in this scenario, yes, I'd have to pay to have the other tire replaced... However, after getting certs... In this same scenario, DT let me use the treadware warranty on the other 3 tires on my AWD vehicle. Not quite the same as having the other tires replaced for free, but still MUCH cheaper than out of pocket.. They told me since I had certs, they didn't have a problem doing this... I've done this several times at different locations with different AWD cars...