"However, the dash in my 1990 Accord lasted 14 years and still looked new when I sold the car. Never was in the garage a day. UV and plastics are known quantities. If a manufacturer cares about the durability of their product, then they can easily deal with the issue constructively."
Please consider that the auto glass in your Honda effectively blocks almost all UV sunlight so that is to be expected. Quality plastic will last longer but the sun will "win." Guns will not be exposed to constant sunlight so the plastic should not be an issue and can be replaced if necessary.