The Duo-R's are generally quite good and often don't need a recap. Of course the day will come when it will be necessary but for all you know the existing caps may last for many years to come.
Even doujindance (the guy who sells re-furbished Duo's on eBay) doesn't bother with recapping Duo-R's. Everyone seems to think he does, but he doesn't, he just fits a new CD lens.
So in short, if everything is working fine I wouldn't bother with it, why fix something that isn't broken.