I wouldn't buy a car that was on long life services. Although 12k would be fine I'm sure but no longer.
I just don't think they are good for the car in the long run.
Mine gets a long life service every 6/8k roughly(sounds daft I know)
It's on 30k now and has just had its 4th oil change, 2nd haldex change, 2nd brake fluid change and the belt/pump done.
Check with Audi to see if it was done between times but the book was not stamped.
For me it would be a no but I'm super picky!