We need to address this, because it's simply not accurate.
Eight years is the federally-mandated (US) warranty period for EV batteries. In California, it's ten years.
Tesla has a policy where it will replace any battery that falls below 70% capacity during that warranty period free of charge.
The majority of 2012 Tesla Model S vehicles are still on their original batteries.
Tesla claims 88 percent battery capacity after 200,000 miles (13.3 years at the national average 15,000 miles per year driven). I'd be skeptical of manufacturer claims, but independent tests and real-world data suggests that's accurate.
In fact, Tesla owners who've put 300,000 miles on their vehicles report an average of 80% battery capacity.
There's reason to believe most EV batteries in mass-production cars will do as well.