ANDY4004, is it 60 miles or is it 70 miles? Big difference, as 60 miles is no sweat if you're even slightly careful even if it's all Interstate, but 70 miles you need to start being pro-active. Don's recommendation is right on:
keep your speed way down and you should be able to get to your destination with a couple of bars remaining. Simply let the car fully charge with the charger shutting itself off just before you leave. I would not try to charge it again once it has stopped (there's even a caution about this in the Manual). You might read up on
hypermiling and perhaps put a few of those tricks into practice. Do you have an opportunity to stop for coffee and a partial charge along the way, and are you time-constrained? If you're time-constrained, I wouldn't bother and would simply take an ICE car. Otherwise, you'll have a nice mini-adventure. In any case, don't forget to take your EVSE with you. BTW, where are you located?