This is a quote from another forum on flex additives.
I think we've been misinformed on here.
The mfg's says it is permanent and keeps the paint softer.
"I used to believe the same thing, because sooooooo many people will tell you that flex will 'wear out' of the paint and it's only temporary. Many times they'll add something like 'just phone the manufacturers and they'll tell you the same'. So a while ago I did just that, I phoned dupont and asked them if flex was only temporary. THe guy sounded a bit like he had never even heard of that before, and of course it's not temporary. It lasts, it's permenant, the paint won't return to "original hardness". Just phone the manufacturers and they'll tell you the same!"