If by average purchase you mean average age of cars on the road, you're very wrong. The average age of a car on the road in the US just surpassed 11 years old. This is exactly why the longevity and long term resale of a car is very important. I know I won't even think about an electric car until they ensure it will last at least 10 years without an expensive overall. I'm currently driving a 14 year old car and have no plans to buy a new one as this one keeps going strong, I have real doubts the same can be said for electrics.