Well, what a refreshing post: you do realize that you are a rarity, owning from new to 240k, right? That usually covers three owners.
Ownership changes distinctly over 10 years- first lease/new car crowd ("what options should I get, whats the residual"), then the smart buyers ("I'm driving a 3 year old car still with a warranty for half the price of new") and then the long termers (all over the place, from "Why is this so expensive to fix" to "I love this car" to "How do a fit larger turbos and NOS") .....Me: 2001 MDX 236k; 2003M5 160k, Q45 245k.... and more
You are a DIYer, so your ability to manage the potential failure should be comforting. Yes, maintenance will be maintenance, no changing that trajectory. In terms of the E70, there is a lot of data here but the problem is that it is not compiled nor really quantifiable- but my sense is that there are 'infant mortality issues' with certain cars/years, but we have not seen a real pattern in longer term failure.
For example, some cars seemed to have high battery discharge issues...batteries would fail, cars not start. Dealers accused owners of not driving enough, etc...but then over time BMW pushed out a specific TSB/SIB on how to monitor the bus for excessive draw. Turns out bad modules would just wake up periodically, turn stuff on, and suck down the battery. My perception is that this is no longer a factor in newer cars.
Diesel. Oh Diesel. BMW F'd this up big time. They just blew it in terms of the SCR system design/execution. Turns out the interrelationships between sensor values, sensor aging and tolerance and error checking within the operation of the system in the broad range of operating conditions was beyond the software that was shipped with the car. It took BMW 3 years and many recalls to get thgis right. I had a 2010 that spent 60+ days in the shop. Lemoned. Now a 2012 that never slept over a single night.
My prediction:
Take care of the tranny. Change the ATF. Dont drive like a racerboi.
Be prepared to replace rubber suspension/isolation points if you want to maintain that tightness.
Watch the cooling system, assume it will need something past 100k
They'll be something- a sunroof motor, AC component, module here or there...before 200k
Finally, I am convinced we can rely on the ability of forums to learn, and come up with more effective diagnostic and repair strategies then what BMW recommends for their dealer network. This happens in the stage 2 & 3 of owners when serious DIYers are faced with $$$ repairs!
My 2 cents
A