JET13, I've almost had an identical experience with my 2008 T2. Currently 390k and 400k should be passed as we're going to Kati Thanda/Lake Eyre next week (with the RossTech in the kit bag just in case).
The driveshaft coupling went at 280k and we replaced it with a Cayenne one for $1200 as the quote for a VW was over $2500! I just changed my AGMs and front ball joints. Other issue was a faulty throttle position sensor which gave a false DPF alert. Recommend Master Auto in Burwood (MEL) as they have several other V10s on their books and understand them very well.
We use our 2012 Golf for anything around the city (180k now without any issues at all) and reserve the Treg for country trips where the DPFs can do their thing. Besides, it is the ultimate touring machine, regularly returning 10km/l and better on freeways, and a limpet on winding roads. The V10 is an absolute bullet when required. I have found BS Duellers H/P to be the best all round performers for 19" (handling and mileage), while I've got Pirelli Scorpion ATR+ 255/60 on the Cayenne 18" wheels I have for trekking - just need to be deflated to fit on the rear wheel carrier.
I've used the recommended oil throughout and I just don't miss any service requirements - not worth it for this car.
They rival the Discovery/RR off-road, but I don't look forward to manually winching it using the eye bolts if I ever get into trouble, given you can't find bullbars to fit and schnorkels would be a (very) tight squeeze. Also, the cargo area is not as accessible compared to the D4 I'm fitting out for some tougher trekking planned next year.