mike, i hear your concerns. but white hammerite, i cant see it being affected anymore than red, especially with 2 coats!
you know how the mk4 anni brake paint faded? as soon as i bought my anni, i repainted them with red hammerite, and it still looks bright red today. that was 2 years ago.
So if i have to recoat the r32 in white in 18months - 2 years i dont mind.