I am completing an 1800 mile tour of Italy and France. My days have not been as long as 100 miles but I did not run out of battery once. On the longest days, I made sure I turn the power off at all stops. I would also use it in the battery save mode when I really didn’t need guidance. It is easy to turn on the screen for a quick look in the save mode. Finally as already suggested, bring a power core type charger and use it if you have downtime as an insurance.