web? you mean nylon strap for flex duct?
If that is what you are talking about You would have to contact each individual manufacturer for that information as it would vary.
I know I used it all the time in attics in Florida with those conditions and never had it "go bad". It is better than metal cause the metal cuts the flex over time from vibration.
Like thehumid1 said, it is different for every manufacturer. There are products out there, like the stuff we are using now, that will still be like new when other structural items in the house have started to decay into thier component molecules.
If more government is the answer, then it's a really stupid question.