Attic flex duct outer gray plastic cover is deteriorating, splitting and falling off. The flex duct is 22 years old now. I can not feel any air leakage thru the fiber glass insulation where the outer cover has fallen off.

If the outer cover is doing this is that a sign that the inner plastic may be splitting too?

Is this a big enough concern to replace all the flex duct in the attic?

How long does flex duct typicalling last in an attic?

Also may be selling the house in the next year or two. Home inspecters will they require me to replace flex duct that the outer cover is falling off even though there is no air leakage?