That's a fair offer from Audi and its dealer and gratifying that it was
made voluntarily. Turbo oil seals usually fail because the engine has been switched off when the turbo is still red hot. No engine oil then circulates through the turbo bearings cooling them, the oil left in there literally carbonises and the oil seals cook. So the rule is always: idle a turbocharged engine for a minute or two after a long ascent, after towing, or after driving on the motorway (don't switch off straight away at fuel stops). If your journey ends with a few minutes relatively slow running though a town at low engine speeds then that will do the job and no need to idle the turbo. Some of the latest petrol turbos are water cooled, so there is less of a problem. Some turbo engines have a system that keeps pumping oil through the turbo while it spools down after the engine is switched off, so no problem with them.