The current official data on SEAT petrol models is the belt should be inspected at the 60K service and every 20K after. If required it obviously should be changed and must be changed by 120K.
Additionally if the car is model year 2000 or older the belt should be changed at 5 years regardless of mileage.
However . . . . this is all about to change (see Briskoda forums). SEAT will soon be saying that all cambelts (petrol and diesel) should be changed at 4 years regardless of mileage.