A few days ago, Elon Musk said in a reply to fan tweets that the Tesla Model S could have achieved a range of 600 miles (965 kilometers) a year ago, but this would make the product worse. Later, he added that the range of electric vehicles is too high to make sense.
In Musk's view, the increase in range is essentially achievable with an increase in battery capacity, but this means that the vehicle needs to carry a larger, heavier and more expensive battery pack. This is actually not "needed" because the current 405-mile (652 km) range is more than enough. In addition, larger batteries can also significantly affect vehicle performance as well as handling.