Every car will be differently obviously but my 2011 GTI now has 165,000 miles on it. I've never had DSG issue in that time, although it's worth checking that any cars you are looking at have had the DSG oil and filter change at 40k mile intervals.
I took my car to 100,000 miles on the original chain and tensioner. I was monitoring the chain stretch using VCDS and it did extend. I found a link on the Briskoda forum which showed at what value you should start to be concerned and I hit that number so bit the bullet and got the chain changed and the latest revision tensioner fitted at the same time. Yes it was more expensive than a cam belt change would be but then I'd imagine a cam belt change interval to be more along the lines of 60k miles.
I bought my car at 36,000 miles and have obviously piled them on since then. It's taken that mileage in it's stride and I certainly wouldn't change my decision to buy one!