Many plastics are NOT really UV stable, and depend on added plasticizers, UV blockers and dyes. Generally, black polyethylene is UV stable for at least several years. But Chinese manufacturers can and do manufacture all sorts of stuff that LOOKS like it's decent material, but is really trash. I've been burned so many times, that I have a pretty negative attitude toward anything made in China.

My guess is, if you get a solar panel manufactured from US made tubing . . . it will last. Otherwise, not so much.