Glue line

During a car wrap workshop in May, Steven Jackson explained that calendered vinyl is more prone to shrinking than cast vinyl and that shrinking can produce a glue line, also known in the vernacular, as a snot line.  How bad could it be I asked Steven with some trepidation?  He said it depended, among other things, on the size and age of the material.  As luck would have it, we recently installed a sign on on a store-front window next to a round vinyl sign that was about 3 1/2 feet in diameter (the sign on the left in the attached photo glue%20line1.jpg).  We were told that the sign was about 9 years old.  A closer examination revealed a glue line around the outside of the sign that was about 3/8" wide (see attached photo glue%20line2.jpg).