Originally Posted by
Matt Hawley
had plastic strips covering the self adhering strips.
Hopefully, you do not mean exactly what you wrote.
If the plastic strips (which are on the underside of the shingle on top) is "covering" (i.e., exactly over) the sealant strips on the shingle below, then the shingles are installed improperly, or, (and this is highly unlikely) the plastic strips were placed in the wrong location at the factory. I say highly unlikely for a couple of reasons, a) because the shingles all go down one production line, and to get the plastic strips applied at the wrong location, the shingles would get all mangled up, and, b) that would mean the plastic strips were not over the sealant strips on the singles below when the shingles where stacked in bundles, meaning they would most likely have sealed together and would have torn the shingles apart when the installer tried to separate those stuck together shingles.
Regarding the plastic strips, they will, along with everything, eventually deteriorate. But not in a long, long time. While they are not made to be sunlight resistant, they are not exposed to sunlight, thus they will be there a very long time. I've seen old shingle roofs ripped off and the plastic strips are still there and intact, because they are basically never exposed to sunlight.
Those plastic strips, if placed properly at the factory, will not interfere with the shingles adhering together once the shingles are laid.
*IF* you are positive the plastic strips are aligned with and over the sealant strips, I would take a photo and send it to the manufacturer, include a tape measure in the photo so the manufacturer can tell the location of the plastic strips to the shingle, if they were manufactured incorrectly, the manufacturer will most likely replace those shingles - those shingles would be "defective".