They're not guaranteeing failure in 5 years, but are pretty sure it won't fail. If "pretty sure" is 98%, then that's 100K (or something like it, probability maths is hard).
Seriously, what do you think a guarantee is?
If these O-Rings rupture, we will replace them under warranty.
Ah, so you're thinking of a guarantee like a politician would use the word. "I personally guarantee that..."
Every time I hear them say that on TV I'm thinking, "Really? So, what are you going to give me if it doesn't work out? What's that? Nothing?! Then it's not a guarantee is it! You might as well have said you pinky-promise, it would be worth as damn much!"
And then my wife tells me to calm down and stop ranting at the TV.
> If these O-Rings rupture, we will replace them under warranty.
See, that's a guarantee.