I don’t normally keep my cars beyond the new car warranty period, but I so like my A4 Avant, I decided to soldier on with it for a fourth year. I took out an extended warranty just in case and at the end of the fourth year the annual service identified a cracked thermostat housing with consequent loss of coolant. It cost £97 to fix, but as I have a £100 excess I paid for that. Nevertheless, lesson learnt - my hitherto reliable A4 is fallible. I’ve decided to keep the car for a fifth year now and so I took out the extended warranty again. Two weeks into the new warranty period and I get a warning message on the DIS that there is a brake servo problem. The diagnostic procedure suggests that the pressure sensor on the servo has packed up, but the technician has checked the wiring and the sensor itself and can find no faults, so the conclusion is that the servo has failed. The new one is on back order and will cost £1500 (actually closer to £1600) to replace. So, if you fancy keeping yours beyond the manufacturer’s warranty period, I would strongly advise an extended warranty as these Audis are not cheap to repair. With the £100 excess mine cost £372 which I consider good value for money given what has happened.