The secret to a lasting finish in the heat is all about the quality of the clear coat and the temperature control during the drying phase in the booth. If the paint is baked at the wrong temperature, it becomes brittle and will eventually start to flake off when the metal expands and contracts in the afternoon sun. You also need to make sure the painter knows how to blend the color into the adjacent panels so the transition is impossible to see with the naked eye. Most cheap shops skip the blending step to save on materials, which is why you see so many cars on the road with mismatched doors