That Elastic band is somewhat more engineered that a piece of rubber.Would you be happy trusting an elastic band to hold up for 4 years?
the Manufacturers have specifically designed the belt to carry out the function it is intended to do, they advise the Belt is good for 8 years 210km, that manufacturer will have included a margin of safety in that design.
the fact is if I live on the continent the Timing belt will apparently last longer according VWGmbh service schedule I.e the whole of Europe vs 4 years for VWUK.
Do you not find that a bit strange.?
of those two belts you had fail : what mileage / age were the belts
I am yet to hear of a T6 with a failed Timing belt within 4 years