I think that is giving them an easy excuse. Properly designed hinges wont squeak unless the bushing material is completely worn out. Think about your suspension, it cycles a ton every day and gets coated in all sorts of gunk. It's rare for them to squeak. A door/tailgate hinge can easily be designed to the same standard.They are probably gotten filthy and washed daily since late summer equaling a years worth of washing every month and causing the hinges to loose lubrication. A drop of light weight oil at each moving hinge would likely solve it and IMO would be expected a few times a year with heavy use.