I agree that in general, it probably doesn't make much difference in the long run. However, if charging to 100% allows for the possibility of _skipping_ the first supercharger, then yes, charge to 100% every time.
I regularly take a trip that's 309 miles total; 2 superchargers along the route: 1st at 112 miles, next at 196 miles. I charge to 100% before starting, then by the time I'm nearing the 1st stop I can use the Wh/mi data thus far to see if I need to stop or not. Depending on weather conditions it's about 50/50. The times I can skip saves lots of time (not just charging, but exiting the interstate, parking, etc)