What are your expectations? If you expect the gold plating on a rep to last as long as the plating on the genuine, you may be out of luck. A rep is only a rep.
Having said that, the plating on my rose gold Pam 147 from Joshua shows no sign - whatever - of wear and I wear it a lot.
Best idea... talk to your dealer. Ask him how long he is prepared to stand behind the plating. Don't be surprised if you don't get a 20 year guarantee. Be reasonable.. at rep prices, you can replace your watch annually... and still be ahead of the deal, had you bought a genuine, instead.