You are a very rare customer. Most people take a break after driving for a few hours. Might as well charge the car. A fast charge speed that lets you drive a few hours on 30mins of charging and you don’t really need more battery capacity than that. Which is pretty much what new EVs already offer. It’s more likely that the cars will start getting lighter as the battery tech improves, a 600mile battery capacity really wouldn’t make a lot of sense for most customers.