I know a lot of people here use it as a top layer, but I'm curious about using it as just a stand alone. Right now I have it used as a top coat on two cars that have a base coat of 601, 105 and then AW and it last damn near forever. But I'm lazy on the other cars we own and I would just like to know how long it would last if it's just stand alone on two cars that aren't garaged and see bay area summer weather (80f-90f, sunny, temperate) or is it worth spending the extra time and doing it right, not that we car much about the other two cars but still.