I did some by sanding/scuffing the chrome then used epoxy or self etch primer (can't remember witch) before trim black paint. They have held up very well for me over the past 15+ years and I would easily estimate 50K miles. Prep them properly and you should be fine.
The best thing is that these will never have that "sagging, dip " look to them. The chrome plastic holds up better than the black plastic. Worst case scenario in a few years you may have to touch them up, but the shape will still be there.
I gave mine a light glass beading (held them about 12" from the nozzle) made it quick and easy to get the inner contours. Wiped with acetone and used vht satin black epoxy paint. Good prep is more important than expensive paint