I think you're better off never putting anything on exterior trim
i agree if the vehicle has been treated right from the start and the trim has either been coated with something like 2.0 OR kept up on a regular basis and protected with less permanent means, like spray wax or opti-seal, stuff that will protect it from UV.
but, a lot of vehicles have not had protection from the beginning and the wear and tear from environmental abuses has already taken place.
particular vehicles that come to mind - wrangler flares, cherokee flares, avalanche cladding, mini cooper flares, 8th gen honda civic cowl/gutters, older element pieces, several gens and trims of the CRV, the unpainted tacoma flares...i'm sure there are tons more i'm forgetting
you need to restore first, which is what i do with that MEDS Renu Finish stuff, then you need to protect. there are tons of ways to do that, some less permanent, some truly permanent (like 2.0).
