Get the belt done. It has an age limit for a reason. They do break down over the years. I’m a mechanic, I know the damage that can be caused if it breaks. Diesels have such close tolerances that if the belt snapped, the valves and pistons would smash together and then you would need a new head, valves, pistons….. The list is endless.
My 04 TDI Cupra has a 4 year or 60,000 mile limit on it. Not sure if your engine is the same, I know earlier models were only 40,000 miles or 4 years. Don’t question it, just get it done.