While my VW diesels aren't TDI - I regularly every 30-40K miles change the timing belt and valve cover gasket - cheap insurance $45CDN and takes only an hour. The damage caused by a broken timing belt is not worth the cost of NOT changing frequently. As an aside - every 60K miles I also change the idler pulley for the timing belt and the crank gear & bolt for the timing belt as they are known to fail after this mileage. The gear/bolt loosened on my wife's 94 causing $1500.00 in damage including rebuilding the crankshaft. There is only a half-moon key holding the gear onto the crank and when the bolt loosens from vibration - the end of the crank shears off - not the key on the gear!There is a new improved 12 point bolt that comes with the new gear. Hopes this helps someone.
Maurice