"How often does it need to be changed?

4 - 5 years (4 years for cars registererd before September 2009, 5 years thereafter). This may need to be changed sooner for high mileage drivers. "

Aye, totally agree with this. I used to work in a VW dealership and we always used this schedule. Even though the OP hasn't done the recommended 80k miles, the belt is due on age as it's 4 years old.

It's not just the mileage that causes wear, but the belt, tensioner, idler pulleys etc will deteriorate with age hence VW quotes a mileage OR time replacement schedule.

Personally, I'd replace the whole kit before the recommended time / distance just for piece of mind. Don't forget to get the coolant pump replaced at the same time, it's run off the timing belt and is subject to the same mileage / age related wear as the rest of the timing kit.

I'd say that it is a bit too soon. If the manual says 80,000 miles then that should be easily achievable. VAG belts are not known for premature failure to my mind. Plus it is only four years old, so not particularly aged.

Consider that most Ford cambelts are 100,000 miles/10 years, yours at 45,000 miles is hardly worn.

I put my post on because I have been through this with VW UK when the dealer said "your car needs a cambelt kit doing".

The service book says "however many" miles, and you'd think that this was all there is to it. However, the extract from their web site says 4/5 years. You can't argue that this advice is available, so; ignore it, have a failure and claim from VW. I can imagine what the response from VW will be.