I send my plastic out to get bead blasted and primed with an elastomeric waterborne primer. Even with that I sometimes get small spots that peel up when I mask over it, but I do a lot of taping on my paint jobs. I did try fusion just to see how it works and its not to good . Our plastic is made from polyethelene which is not meant to be painted. Period. What I do is a crap shoot on the longevity. If it doesn't get scratched or a high pressure wash used on it it can last indefinately. Its when you scratch them and roll them in the sand you start having problems.

 

Ive had my plastics painted by crazy for a long time and ive wrecked alot lol and the plastic still has held up well.