I don't agree with the service intervals that Audi recommend, 11,000 miles between oil changes, should just about get you out of the warranty period.
I wouldn't mind an A8 around the 2009 / 11 period but the mileage is getting a little high at that age.
If I traded my 2009 A6 C6 Avant in for one, I would never get what it's worth to me.
It's a genuine 42,000 miles from new and the longest it's ever gone between oil changes is 4,000 once, usually around the 2,000 mile mark, oil is cheap enough to change it yearly.
Always garaged out of the sun and rain.
I purchased it from Stafford Audi.