Film protects a coated surface in transit and on the line. Left on too long, it does the opposite. The adhesive is designed to release cleanly for a limited period under normal indoor conditions. In a container standing in the sun, or a warehouse with a metal roof, surface temperature runs well above ambient and that period shortens sharply. The result is adhesive transfer: a patchy residue that has to be removed by hand, and in bad cases a gloss difference that cannot be removed at all. On textured and matt finishes the marking is worse and less forgiving. Film also changes how the panel behaves in forming. It adds a layer between the tool and the coating, which is usually helpful, but on tight radii it can pull the coating with it when the film releases unevenly. If the part is laser cut, film near the cut edge melts and leaves a hard residue that solvents struggle with. The working rule is simple. Specify the film type and the face it goes on, specify a removal window in weeks rather than months, and store panels indoors and off the floor. If a panel is going to sit in stock for a season, it is better to ship without film and pack with interleaving than to leave adhesive cooking on the surface. First in, first out is not an inventory slogan here. It is a coating specification.