The average age of operating automobiles in use within the US is closer to 12 years. The registration fee (annual renewal, not initial registration) in the US is based on vehicle value in 8 states by my count.

On a personal note, me and most of the people I know think more in terms of miles than years. I figure every car I buy is good for 200,000 miles and most of the brands I favor have another 100,000 miles of life beyond that before repairs exceed some loosely calculated rate of return.