Driving style also has a big effect on range. Power needed to maintain a constant speed is a square law function (proportional to speed squared). This post provides a bunch of data on Tesla models:
Range of the Tesla Model S/X/3 at 65/70/75/80 mph ♞. As you can see, it is possible to exceed 310 mi by a fair margin, but this requires what some would start to call hypermiling. Before you ask, the same physics applies to ice cars. It’s just more noticeable with EV‘s since they are already so efficient, incremental improvements in factors such as driving style are more obvious. The good news is that if you ever find yourself short on range, you can simply slow down and get more miles from your remaining charge.