You can get a little better gas mileage at 65/66 vs 70. I usually set mine to the fastest speed I can (around 65 level and 66 downhill) that keeps the cruise coach bar in the blue, too fast it turns yellow and less than 1/2, more air drag the faster you go.
You can also get better mpg if you use eco cruise and let the car lose some speed up hills.
If you want to be more involved in the drive, you can also get better mpg or mpge if you don't let the car speed up down hills and instead recharge the hvb harder by using hill assist or L in some cases. On the side roads at cruise of 38 for example, you may find that you need to disable cruise just before the crest of a hill as the car will overspeed automatically down the other side not knowing that the road suddenly turned downhill. Once you're on the down slope and the hill is not too steep, re-enable cruise. If its steep then disable cruise and turn on hill assist at the same time, once the hill is leveling off, turn off hill assist and re-enable cruise.
All those little things you do add miles to your EV range, and you might end up going from 17 miles to 27 miles range even with the AC on, with the AC off it could be 30 miles per charge, certainly not out of the question depending on how you drive.