people say around 100,000miles, but VW say they will last the life of the engine, its not the chains that break, but the tensioners crack and fall to pieces as they are plastic mine is on 140k, i bought it on 130k and its not had chains done. Is a case of when they become noisy imo, i've heard of VR's doing over 200,000 on original chains and tensioners. i only asked about headwork as some of the Vr's i viewed before mine that had had the chains done has also had the lifters and valves done too