Ok, I left the house 48 minutes ago for a run with my iPhone 6s battery level at 5%. I had iSmoothRun and GPS running the entire 45 minutes to log my run. The battery level is now 3%. I have learned that, since my iPhone 5, the battery level shouldn't cause me any concern until it dips below 5%. Until then, I can go anywhere without worrying that my iPhone will die. Thank you, Apple!