I also have the "certificates" .. after running over a curb, and blowing tire and ruining rim.. I questioned the reason I got them since i had to buy another certificate with the "free" replacement, but after running over a 16 penny nail and not being able to patch (corner tread/sidewall)..

I was happy`to buy another certificate with the "free replacement". At 140 a piece without certificates..

I think the total bill was 730 dollars for the original 4 with tax and all the rest of the BS. but I am pretty sure that 6 x 140 plus tax is a bit more then that..

good luck