Go with manufacture recommendations as specified in your handbook. They are best placed to know what they're talking about. VAG cars that are designated variable service intervals are supposed to be clever enough to know when they need an oil change, subject to the 30/50k limits.
My own approach is probably best on balance - use the so called long life oil and change it at 20,000 kilos unless the car asks for it sooner - very unlikely. However, there are probably trade offs in using the long life oil - although, last time I checked the same oil was specified for VAG diesels with DPFs on fixed service intervals - i.e. the thinner consistency provides less protection for cold starts and such like. That seems to broadly concur with the following advice from Volkswagen:
https://www.volkswagen.co.uk/owners/servicing/regimesAs a Volkswagen owner, you will already have experienced the pleasure of driving a car that's renowned for reliability. So when it comes to servicing it, why settle for second best? Visit your local Volkswagen Retailer or authorised repairer who will be ready to help you every step of the way. Their staff are fully trained in every aspect of servicing to ensure you continue to enjoy mile after mile of trouble-free driving.
You can choose from two types of service regimes, depending on your driving methods.
Fixed Service (Time and Distance)We recommend this service if you are likely to drive less than 10,000* miles in a year, and if you tend to drive in the following way:
Mainly city centre driving, short journeys with frequent cold starts
High engine loading activities, e.g. frequent hill climbs, driving with your vehicle fully loaded and towing
Uneconomical driving using high rpms with heavy acceleration and heavy braking.
Flexible Service Regime (LongLife Service)We recommend this service if you are likely to drive more than 25 miles a day, and if you tend to drive in the following way:
Regular long distance driving
Driving at a constant speed with minimum vehicle and engine loading, and minimal towing
Economical driving
This Flexible regime has been made possible due to the development of new Volkswagen engines with the latest technically advanced longlife oil. These engines use built-in sensors that continually monitor the oil quality, making it possible to enjoy reliable and confident motoring for up to a maximum of 18,000* miles or 24 months (whichever occurs first).
*Please note that all mileages are approximate as the service indicator system uses kilometres as the distance measurement.