Black plastic and sun = fade. I've never been able to stop it, maybe someone else has. If you treat the plastic often enough you might be able to stop it but waiting 90+ days with it sitting outside, especially in W TX, it is going to fade.
I keep my trailer in an enclosed building so I've eliminated that problem. Before I did I used Armor All - doesn't work except for when apply plus about a week. Waxes etc., same thing. I began using 303 and it worked the best of everything I tried. Now I use it on the entire RV with good success. Even with 303, and the trailer subjected to high doses of heavy sun along with the elements every day, you need to put it on about every 60 days or something will start to "age" as best I can tell.
As far as Amazon "mixed" reviews; I just did a quick scan of 303 on Amazon and the ratings were 4.5 - 5 on everything I looked at. To me, that's not too "mixed".
https://www.amazon.com/s?k=aerospace...b_sb_ss_i_1_10