I bought my Mk6 from a dealer with replica Monza Shadow's on. I did'nt know at the time they were aftermarket but after around 6 months i noticed whiteworm appearing around the holes for the studs.
Got to about a year I contacted the dealer to complain, they were fine and totally upfront about them putting on aftermarket (the car originally had 17's) but offered to refurb them for me FOC. Being diamond cut they ended up painting them and they turned out looking great again.
Don't know how long they would last though as i got a Mk7 as a loan car for a couple of day's but took it back to a cracking offer for mine and into a new Mk7