Operated a colour lab for many years and used cold mounting & laminating exclusively. Never had problems with the mounting of prints, with laminating films the prints had to be DRY. Also PVC based laminating films were very forgiving, polyester films were not and if the material being laminated was not dry could form bubbles and creases when exposed to warm/very dry environments. When mounting backlit material or face-mounting prints to plexiglass the same problems were there, acrylic material was more forgiving than polycarbonate, although outgassing from acrylic in hot lightboxes sometimes caused problems. The key to success was to be knowlegeable about the process. The answer to the original question is Yes, they are permanent if properly chosen and applied. Luigi at Drytac in Toronto is The guy to ask for advice, for both ot & cold mounting & laminating.