Bentley (93~97 A3) shows the ABA (2.slow) had a "60,000 miles, or every four years". Note: My early 97 issue of Bentley does not have the AHU information.
Bentley (95~97 B4) shows the timing belt (ABA, AAZ, 1Z) had an "Every two years regardless of mileage" interval plus a "Replace every 60,000...