YorkMan – As per your original question, you do not have to keep the car for the full extension period, so it might be best to extend for 2 years. You can still change the car at any time whatsoever within that 2 year period, but if you did end up going the full 5 years you get £900 GCB whereas if you change at 4 years I think you get the same £600 GCB as if you changed at 3 years. Mileage seems to have very little bearing on it. Our car has done 30k miles and Motability were happy to extend it. In the end we decided to change, as the way the scheme is going we can see the top end cars that we like now not being available in a couple of years time.