Yep, it sounds like you understand it. I like to make the actual consumption rate match what I planned to consume as follows:
If the next CHAdeMO station is 110 miles away, I want about 125 miles of range (10% - 20% extra). With a new battery at 70F battery temperature or above, I will need 3.4 miles per kWh with 37kWh onboard (about 90% of a new battery, or a fully charged battery that is 10% degraded) to have 125 miles of range.
You can get this data from the range chart:viewtopic.php?p=251#p251
So, then I will look at the range chart and determine that I need 65mph on flat, no wind roads, without cabin heater to generate those 3.4 miles per kWh. But, I'm always going to start out below that speed to allow me to perhaps speed up at the end. It's a real drag to have to slow down at the end!!!
You always have to adjust for elevation from start to finish (1.5 to 1.8 kWh extra consumed per 1000 feet higher at destination than start, depending on vehicle weight). Therefore, driving from sea level Sacramento to nearly 7000 feet Lake Tahoe will consume an additional:
12kWh = 7 * 1.7kWh
That means with 37kWh onboard, we have to adjust:
25kWh effectively onboard = 37 kWh - 12 kWh
So, to drive those 110 miles up a 7000 foot mountain requires:
4.4 miles per kWh = 110 miles / 25 kWh, or about 45-50mph up the hill, according to the range chart.
So, for my journey of 110 miles on a level highway, I will start out at 60mph. I will monitor the performance every 10-20 miles. I reset the energy consumption meters (both pages) and reset the trip odometer, and I'm off.
If, after 20 miles, I'm no where near 3.4 miles per kWh, it's time for some action. I'll slow to 55mph, and monitor in 20 more miles... did it start to trend upwards at all? If so, I'll stay at 55mph until reaching 3.4 miles per kWh. If the consumption is holding steady at the lower value consumption rate (below the planned 3.4 miles/kWh), or still trending downwards, I'll slow to 50mph (and start thinking about Plan B recharging spots).
This is why I won't normally plan to drive below 65mph, except in exceptional situations. If I'm within about 40 miles of the destination, I can start eating into my reserves by speeding up or turning on the cabin heater if I'm cold.