Jim Fitzgerald wrote: IDK, but you could get a backup battery. I have a couple Anker batteries in my flight bag. If my flight is going to exhaust my Nexus 7 battery, I plug one in from the start.
Yes, I also have a backup battery. The other option is to plug it into aircraft power. I have been told, Foreflight allows the iPad to sleep. I have two reasons for the question. First is to understand power management. Second is to allow the iPad to cool down when you really do not need it. Thermal shut down of the iPads during aviation apps is very common.