If they're not the updated ones with extra strain relief I'd recommend new. One of my stock lines deteriorated internally and prevented full pressure at the caliper. After ruling everything else out ordered a new brake line (front right) and you could immediately tell it's better made. After replacing it my front right brake started working properly again. It's a similar problem to the HPFP feed hose.
A forum community dedicated to all Volkswagen owners and enthusiasts. Come join the discussion about performance, builds, modifications, classifieds, troubleshooting, maintenance, new releases, and more!