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I'm now wondering at what point and on what types of trips it's actually faster, to drive slower, to get to your destination without needing those pesky charging stops.
My recent experience with a 1400+ mile road trip (each way) in a cannonball / stop as little as possible / drive through to destination type road trip, was that our balance point between charging time and driving time (in a 90D Model X) was somewhere in the 75-80 mph range. We'd go faster when we were charging into the 75% range and then stayed an extra 5-15+ minutes charging more than we needed, and we'd slow down below 75 when road conditions changed or we didn't really stay long enough and the buffer was getting uncomfortably low. The idea when we had more range than we needed to the next charge stop was faster got us there sooner, and the incremental range consumed was nearly 'free' from a charge speed perspective (bottom of the battery is 7 miles/minute, while the charge rate is more like 2-3 miles/minute at the 75% mark).
The tricky part isn't the speed per se - it's the slow down in the charging rate. In our Model X with a max charge of about 255 miles, the charging rate would slow down a lot by about 200 miles of range. Still ok (2 miles / minute kind of speed) up through about 210, but you could easily spend 30+ minutes getting from 210 up to around 240 - it REALLY slows down there.
So as long as the next stop was in 80 miles, then charging fast to 150ish was usually accomplished during a minimal human stop for bathroom and a drink (iced tea for me!), and you could go as fast as the road and traffic allowed (don't need to watch the range remaining at all). For a 120ish mile segment, charging fast into the 180ish range was also pretty good.
But for a 200 mile segment, the charging time becomes a pretty serious impediment (probably charging to 240-250 to allow buffer and weather/elevation gain/ stuff).
All of which shifts dramatically in one of the bigger battery / more efficient cars with say 320 miles of range. The fast charging will still be in effect all the way through 240ish or so, which means even a longer segment of say 200 miles can be charged for in a timely way.
The big balancing point, from that experience, was doing as much charging in the 7+ miles/minute range (bottom of the battery) that was still going quickly at the mid point and a little past (say 5ish miles/minute). And ideally, you want to be ready to go when the charge rate is getting down to 3 or 2 miles/minute. For shorter segments, human readiness was mostly our limit. For long segments, a bigger battery to enable a fast charge into ready-to-go range would have been a big time saver.
The other thing that was pretty crazy to me, was that even with the cruise set at 80, the difference between rated range and actual consumption was pretty small. We might have used 90 miles of range to cover 80 miles kind of stuff. The aero on Model X is amazing (my experience anyway). The noticeable bite would happen when we moved the cruise up to 85. And yeah - going slower definitely extends range in most weather - the noticeable difficult balance point being really cold weather where you need cabin heat (as cabin heat is a more constant draw based on time, rather than ground covered - in that case, faster is better strictly in the context of the cabin heat).
