Cam belt replacement - age or mileage?

My Volkswagen Tiguan, owned from new, is almost five years old but has only covered 26,500 miles. Volkswagen say the cam belt should be replaced at five years or 100,000 miles but cannot tell me why the replacement is time-related, only that it is an 'advisory'. Can you please explain me why a can belt replacement is time-related.
Volkswagen is giving you good advice when it comes to age but I would shorten the mileage to 60,000 miles.

The pulley will degrade over time and can force the belt off. The rubber within the belt will also suffer age-related wear, which increases the risk of it snapping. Given that a cam belt failure will wreck the engine, I don't see the point in taking the risk.

Most cam belt problems we hear about occurr when the car has covered 60,000+ miles and/or when the belt is over six years of age.
Answered by Dan Powell on

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