And on the subject, just yesterday we had our tires changed. They have been garage kept since day one, always well aired up, looked great, and showed no signs of wear at all, yet the date codes were from Aug '07 and I thought that was probably long enough.
Could we have pushed them another year? Probably, but why? Lets say I got an extra year on this set and another extra year on the next set. Thats 2 extra years over an 18 year span. It's just not worth pushing it IMO. As noted in the OP, bad things happen fast when a tire goes down.