Even after extended wear, your timing belt should never stretch. This throws off your engine timing and results in increased fuel consumption and emissions. If your timing belt snaps, the pistons will strike the valves that are left open, bending or breaking them. At the very least, the new cylinder head will have to be replaced. Worse, it could cause engine failure in a matter of seconds.
Service intervals vary depending on the model and engine, but usually start at 90,000 km. However, the timing belt should be replaced at least once every 6 years along with your water pump to take advantage of cost savings.
Volkswagen Original Timing Belts are made of high-strength synthetic and glass fibres. They have a wear-resistant coating and can withstand the rigours of tough, frequent use, temperature fluctuations, and moisture.