My rule of thumb for second hand cars has always been <4yrs old and <50K on the clock, with only one private owner. But there's nothing vageuly scientific behind it, it's just my personal comfort zone. Most 7yr old cars will probably be fine for another 5 years, unless it's been badly treated (i.e. company car driven everywhere in second gear by resentful sales reps). Audis are good cars for sure, but you're paying a large markup for the brand. Seat/Skoda/Honda/Toyota all good cars and better value for money.