One thing to keep in mind with car tires - the extended warranties aren't valid if there is uneven wear. So, if you hit a pothole and your car gets un-aligned (happens a lot), and you get some uneven wear before you notice it, you might not be able to exercise the warranty. Also, if one fails at 85,000 will they replace one, a pair, or all? Most cars require that at least 2 tires be replaced at the same time (for wear issues) - 4 if it's AWD. So, if one fails that late, you might get a free one, but have to pay to replace one or more.
I'm getting ready to have to replace mine too - but haven't started researching yet. I hate, hate, hate dealing with car stuff.
As far as lifetime - I would think at least 150k for an average car (we tend to get more than that out of ours). Kia has a fairly good rep for longevity, IIRC. I gave my VW Golf to my mom at about 175k, and it now has ~225k (despite the fact that she doesn't believe in car maintenance - guess that's easy for someone who has never actually had to buy a car - snort).
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