My experience is limited, but the best durability I have gotten from a trim product is Ultima Tire and Trim Guard Plus. It's a sealant that dries clear. When I used it on my wife's 2005 Taurus it made the plastic side view mirrors look and windshield cowl look much better. I'm using it now on the cowl of my S2000 and CR-V--looking good.

A little of the stuff goes a long way. This 12 oz. bottle of mine is going to last me forever.