I have C4 and DLUX for my own (and my family's) cars, but I've been impressed with the TW Endurance trim coating for cars I don't see too often. I just ordered Black Wow Pro for that same purpose -- I have a couple of SUVs to do, with tons of faded cladding. People who pay me to clean their cars and make them "shiny again" aren't overly concerned with a product's longevity, and many -- if not most -- silicone- or dye-based products provide that initial impact and last long enough without a sudden failure that people don't seem to have complaints.
That said, the TW Endurance seems to perform similarly to their tire coating, fading gradually and gracefully over the course of several months. It's so good that I have to remember to which cars I've applied it so I can reapply it when they come back. I'm hoping the BWP is that good because at the sale price I paid, it should work out to a few cents per car, and maybe a couple of bucks for an SUV like the Element.