What mileage to change cam belt on Audi A4 1.8T?

Answer: Long enough before it breaks and destroys your engine, so you can sleep at night. Audi recommended "90K miles" .... but they backed off on that figure when belts started breaking @ 60K miles. For a good night's rest, check the belt for signs of wear or checking @ 40K miles. If it's still like new, then replace it @ 60K miles .... IMHO. This is one area where an once of prevention is worth a ton of money.

Audi recommends every 75,000 miles.