I think luck plays a big part of it, but if you keep on top of them (i,.e touch up any chis etc immediately with touch up paint and / or clear lacquer, then barring a catastrophy, you should be OK.
My old MK7 GTD with the standard Diamond cut alloys were still mint when I swapped it for the current GTD after just short of 3 years, but then I've heard of others that had had issues within 12 months or so. You certainly need to keep on top of them.