I really can't think of a good technical argument for extended oil changes - I can though think of plenty of good sales and marketing reasons why! - just do it every year/or 10 to 12 thousand miles (whichever comes first). I've spent my life in and around motor vehicle workshops and I've seen some pretty expensive examples of engines which have not had regular oil changes. Of course modern oils are vastly superior, especially in terms of stability and additives incorporated in them but you have to take into account that the engines of today, especially turbocharged engines and even more especially small capacity turbocharged petrol engines put demands on their lubricants which were unknown just a few years ago.
I'm especially interested in inlet carbon fouling on Direct Injection petrol engines and have read quite a lot about it. There seems to be an opinion that old oil in this particular design of engine (and nearly all new petrol units are now direct injection) contributes significantly to this
problem. It seems to be that as the oil ages and the additives and polymers age it becomes easier for oil mist to get past the inlet valve stems and through the breather system which increases the rate of carbon build up in the inlet tracts and on the back of the inlet valves. So, far from pursuing an extended oil change interval on these engines, the argument seems to be that, if anything, the oil should be changed more frequently than recommended by the manufacturer. I'm learning more about this insidious
problem all the time so I'll be continuing with my mileage/time based interval for the present thank you very much. As Mr Pig says above, only use the correct VW spec oil for your car too. The actual manufacturer isn't so important - although I like to use a "big" name that I trust (currently I'm running the whole "fleet" on FUCHS) but it's very important that it matches the VW spec for your engine. Currently for me that is a Fuchs 5w 30 to ACEA C3/API SN compliant with VW 504/507. This is actually an oil which can do extended interval changes but by changing at a year/10,000 miles I'm ensuring the oil is almost certain to be still in spec when changed. I actually rang Fuchs tech department and formulated this procedure as a result of that chat.
Not so long ago I would have said you were actually better to buy a cheap supermarket oil (of the correct viscosity of course - that's the 5w 30 or maybe 20w 50, whatever) and not worry too much about anything other than changing it regularly. Indeed many years ago I would do exactly that with my old Ford Anglia or the Cortina which replaced it. Not now though. I might still get away with it on our elderly Fiat Panda runabout but not on anything reasonably modern and absolutely not on anything with a turbo.