For my A3 8v 2.0 tdi, cam belt needs replacing every 70 K or every five years. Whichever comes first.
Yes you can gamble on not doing it but the thing with gambling is to weigh up potential loss versus potential gains.
In my personal opinion, the potential losses ie: engine damage should the belt snap....... Far outweigh paying for the belt change. Had mine done at Audi Portsmouth and got free MOT for the life of the vehicle...... Nice bonus.
I totally agree - it's about weighing up potential loss vs potential gains.
For my 2013 1.4 TFSI, when the service book was printed Audi had decided it was 122,000 or 140,000 miles (I can't remember which) and that time-based replacement wasn't needed. This was years after they'd changed their advice on the previous generation of engines to say "every 4 years or the specified interval - whichever comes first". Since then Audi UK have started to say "do it every 5 years". So I'm not blindly ignoring official advice and chancing it, I'm personally planning to go with what the manufacturer printed in the service book and, as far as I know, the most up to date advice from the manufacturer themselves (rather than their UK distributor).
There certainly are belts designed to last much longer than traditional cambelt intervals (e.g. this specs 240,000km with no time-based interval that I can see
https://www.contitech.de/en-GL/Industries/Passenger-car/drive-belts/CONTI-DIESEL-RUNNER).
But coming back the the risk/reward, that's what it's all about. There's a risk to not getting it done which slowly increases over time. The risk is of a ruined engine. Once I'm beyond the official interval, that risk starts to make me more nervous. There's also a risk to getting it done, in that the garage might damage something else or damage the new belt whilst fitting it (it took 3 visits a few years back before I managed to explain to a Skoda main dealer how to adjust the diesel injector timing correctly after a cambelt replacement). If you got the belt changed every 6 months then I'd say that you'd massively increase the overall chance of a belt failure.
And the reward is not having to spend however many hundred pounds they want for the replacement.
I'm trading off the risks of getting it done and of leaving it for too long against the rewards (money saved and avoiding other potential damage to car by mechanic) and coming to my own conclusion. For me personally I'm happy to go 10 years and I'll think again after that. I'll also revisit if I start to read lots of reports of belts failing on these engines, or if I see official advice from Audi Germany that they've changed their mind and it should be done more often.
What I'm not doing is blindly ignoring the manufacturer's advice in a misguided attempt to save a bit of money! And I'm also not telling anyone else what the appropriate risk/reward balance is for them.