If you keep an electric vehicle 10 years?

Then that means you likely are going to be out 5000 to 20,000 dollars in replacing your rechargeable batteries.

From a practical point of view then it isn't as economical to own an electric vehicle long term because of this. It appears it would be almost more useful to own a new electric vehicle no more than 5 years OR to buy a used one that just had it's rechargeable batteries changed. So, buying an electric vehicle at 7 to 10 years old is not economical or even useful unless it's rechargeable batteries were changed recently (unless you want to pay 5000 to 20,000 dollars in addition to the price of the vehicle that you pay for new rechargeable batteries.

Also, what happens to your old rechargeable batteries? 

Or do they just pollute the earth and ground water?

Just remember that most of the area below your feet in your car is composed of rechargeable batteries.