I've been working on some things for a while, where testing and development is much more rigorous and extensive than some small, middle-class car. Theory, tests and practice are two different things. . Despite what you have listed, cars still break down, their headlights burn out ahead of time, and their bodies crumble to dust due to rust. And mind you, I didn't talk about other aspect of headlight design other than terrible bad heat dissipation.Virtually none. The headlight would have a large interdisciplinary team of optics engineers, mechanical engineers, and EEs, as well as manufacturing specialists. Every aspect of it will have been simulated before a tool was every cut. After tooling and extensive design validation testing, extensive testing for abnormal conditions and extensive accelerated life testing would occur. Then, and only then will it get to the consumer. Things slips by in design, as no test has 100% coverage, but your post is pure fantasy. Your friend and you obviously have absolutely no experience with automotive design, and I expect you have little experience with lifetime prediction of LED assemblies for automotive.
Yes, the body really rots very quickly. The salt on the roads and the climate are taking their toll. 2-4 years and through rust may appear in the body