I've crossed the Continental divide and many other, smaller divides when driving mine. As has been mentioned, in steep country, you get some energy back when descending and don't use any. It turns out to be mostly a wash. Strong winds are much more of an issue, if you happen to be driving against them. The built in range indicator is quite accurate though, so most cases of dead battery are done on purpose or through stupidity. Speed of travel can make a huge difference in range, so if you find yourself in a situation where it may be close, just slow down by 10 or 15 MPH. I've never done this on purpose but by keeping track of how much range grows when in a reduced speed construction zone, the effect is real eye-opening.
Now having said that, a battery failure on any vehicle, ICE or EV isn't something to look forward to. I found myself behind a newer Jeep SUV crossover stalled in an intersection. A Police officer was there and a bunch of others tried to push the vehicle clear of the intersection. The Jeep had one of the turn knob shifters and we couldn['t even figure out how to get the thing out of park. My car has a main high voltage traction battery and a small 15 volt control battery. If the traction battery fails, a swipe on the screen and I can put the car in tow mode, so it can be pushed or drug onto a roll-back. The brakes and steering are all still mechanical or hydraulic link and will work when the motor isn't turning or running.