First I am a former mechanic, I have worked on a lot of stuff, 35 years.
I had ours done with the Timing Belt at 103,000. Some chain noise, not bad, no sudden increase just a slow steady one. Some odd vibrations on start and worse at low idle, would shake the car at times.
Being the inquisitive type and wanting to know and my own trophy, I had them put all the parts from the change out in a tub.
I then did an in depth look at all of them. This is my list of worst to best and the first two could be a swap (I don't have data on what a new chain was like for stretch and bend - doe not matter, more interested in which would fail first)
Chain: This is a fixed pin non bushing (roller) type chain. Its so odd (old tech) I have never seen one used before. his is the worst damned type of chain you can use, its so old tech that they probably quit using it after the Model T.
What should be rollers are literally the bushing. I found 6 areas that had serious wear on the sprocket side (fixed). It might have made 200K. Maybe.
The chain itself had a lot of flex and some stretch. from the flex I would say it was gone. Stretch, not as bad. How long? Unknown, as it turns twice engine speed in is driving a lot of *&^% no idea. I do know they can snap.
BM/OP: While this looked very good, the shaft between the one balance lobe and the Oil pump was failing. The hex was worn on all surfaces on the BM end. It was loose on the Oil Pump end (no wear). Maybe Oilhammer of MoGulf can explain it better. Overall it was very loose. Again, maybe 200k, could go sooner.
The sprockets looked ok and were not sharpened. The tensioner looked ok but looked to have been running out of range of tension (chain stretch).
I did talk to the tech, they have one mechanic who has one with 350k on it and still going.
From what I see on the chain I have no idea why.
To put the chain in perspective,
https://en.wikipedia.org/wiki/Roller_chain#/media/File:Roller_Chain_Render_(with_numbers).png
You can see the pins, what you don't see is the pins are fixed, they don't roll over the sprocket, they slide over.
While I thought there was no fix, a modern chain with the high quality bushing setup would probably last 500k.
Keep in mind the quill shaft failure though.
I understand it got beefed up on the latter BM/OP and that's a plus.
The fact there is no slop in the chain causing a pulsation is a huge plus as well.
Mileage no better, maybe a bit worse. I will take that trade off.
I did appreciate they were willing to install the TDI block heater. Not someplace I can bend into anymore.
I am almost looking forward to winter now, oil heater, batteyr heater and block heater. Happy engine.
Someone maybe can update me on what the Coolant Migration is? Ours has been stellar for no adding.
Suspension is still tight, still running original shocks, probably do the rear next summer.
Brakes were done by non VW (as they would not put the battery blanket on the battery for me)
Some of that I would have tried myself but back not happy with those positions.
Coolant sensor was kaput and I got that changed while it was in.
VW did the work as I could not afford not to have a full warranty and they had referral to VW.
They seem to have done a good job as no issues in 2500 miles (which I know is not a lot)