. . . continued . . .
If it is the case that belts are now failing earlier than expected and there is a sound technical reason why VW have implemented this change then you still have to ask the question why are VW now churning out shyte belts? Why are we taking a step backwards here?
First, Volkswagen do NOT make timing belts. They use ContiTech, probably one THE most highly regarded timing belt manufacturer in the world! 
Next, VWs own 120,000 miles change interval was just pure 'pigs might fly' - simply to artificially create to the motoring press and fleet managers of how cheap their cars were to maintain. Once the Mk5 Golf GTI, and all the associated TFSI engine users 'honeymoon period' was over with the press and fleet managers - then VW sensibly revised their cam belt change intervals to co-incide with the industry standard norms.
But you still completely miss the point. A cam belt change is . . . .
'preventative maintenance' ! ! ! !
So we shouldn't believe VW when they say to change at 120k but we should when they say 4 years? I hope that isn't ill informed cynacism 
Interesting train of thought! But personally, I had absolutely no doubt that 120k was unreasonable - so I never believed it anyway. And 4 years isn't a big deal to me either.
And I think that it is common knowledge in the independent motor trade that 120k is really fairy-tale suggestions, simply to 'suck in' prospective new car owners with the (unreasonable) suggestion of low maintenance costs. Because lets face it, how many 'first owners' (ie orginal owner on the cars V5) actually make it any where near 100k miles, let alone 120k miles. Those kinds of mileages will usually be 2nd, 3rd, 4th ect owners. And even with the more suitable and reasonable 60k change, then the vast majority will still be in the 2nd hand market, so still not affecting the orignal owner.
At the end of the day, I just think that the vast majority of the motoring public simply think that modern cars are actually 'maintenance free' - and so when they get advised of an 'expensive job' like a cam belt, they get all ar$ey. Just ask yourself how many of your neighbours you can actually see lifting their bonnets every weekend to check their fluids, and once a month to check their tyre pressures and exterior lights?
The thing is we seem to be in broad agreement that 5 years / 60k is sensible.
My issue is not at all with those who want to play it safe, especially with such a critical part. I fully accept and agree that changing the belt early is a good thing....but lets not go nuts.
Fairy-nuff. But I still don't think that 4years is going 'nuts', especially when you discover the true history of some of these motorpoint and other GTI imports.
4year cambelt change - nuts? No. Cautious? Yep.
5years would be better - but at the risk of still allowing a high proportion to slip through the net, and not actually get done until the 6year/60k service. Beyond that, and it is a slippery slope.
My issue is with VW changing to 4 years.
Then VW are damned if they do, damned if they don't!
So what if they just left it at 120k miles, and just said 'fcuk-em' to anyone whos belt went?
Maybe the real crux of the issue is that VW Germany now have some 'real world' data (rather than artificial test labs), and it is showing that the belts are failing maybe around the 60k, 70k, or even 80k mark. So even if the belts were letting go at 80k - then to downwards revise it to 60k miles would still be cutting it way to fine. Afterall, I'm sure we all know that when a cam belt fails, it is catastrophic. But it is very different for a spark plug or air filter - so what if a spark plug fails? OK, you may get a misfire, or you might even get the MIL on, and need a tow-truck. The damage to your wallet will only be the very same cost of the spark plugs - a major difference to the effects of a cam belt failure.
At the end of the day, us mere minions will never know the exact reasons why they decided on 4 years - but we should all at least be glad they have actually been sensible enough to be proactive, even if it does add an extra £300 every 4 years to our maintenance bills.
In your experience, as a retired mechanic, how many timing belt failed at or around 4 years (lets assume normal milage) and negating outside influences like oil, failure of some other part. I'm talking about plain wear and tear? I suspect none.
None, absolutely none.
But again, you miss the fundamental issue. Relying on 'experience', if I were to say, test spark plugs, and I tried to run them for 100k miles - then I might say find they were failing at 80k miles. So, reacting to that, first, no other damage was done to the engine, and only the plugs themselves were affected (appart from the associated inconveniences of failed plugs) - I then decide to downgrade the miles. Knowing that they failed at 80k, I might say that to lower it to 70k would be pushing it a little close (to account for any 'rogue' plugs that might fail at 70k) - so I change it to 60k miles. So all things considered and duly amended - I happily run for years, covering multiples of 60k miles plug changes, but still get an occasional plug failure. This isn't really a problem.
So looking at the fundamental issues between spark plugs and cam belts - when one fails, it is catastropic, but the other is just a minor inconvenience. Another issue is the ease of changing cam belts and spark plugs. Most reasonably competent peeps would not have any probs changing their own plugs, even at half the recommended schedule (just like many do with oil changes) - but how many 'home mechanics' will do a cambelt change? The vast majority will shy away, and either send it to the stealer, or to an indpendent garage.
Thats why I think they are treating the customers harshly here by "forcing" them to change their belts - at not insignificant cost - earlier than strictly necessary.
I don't really see any 'force' being used. And at the end of the day, then technically, every single item changed during routine maintenance is 'earlier than strictly necessary'!
But how many peeps do you hear whinging about having their brake pads changed, when they still have 2 or 3 mil of friction lining left?
