Another factor also needs to be considered. Whenever a film is added, that film will have an impact on the battery life. In order to get the same amount of brightness from the tablet with a film on it, you must run the screen brighter which is one of the largest determinants of battery life.
If you are working in a non-air conditioned environment where the ambient temperature is excessively hot (+95F/35C), then the tablet is likely to overheat in any circumstance. Our recommendation is remove the tablet from being in direct sunlight and provide additional airflow to help disipate heat from the device.