If the sensors are on, it will impact battery life as it is looking for them the whole time. Battery life is rated for around 5 hours for GPS/HR/Music, 9 for GPS/HR, 11 for GPS only, 2 weeks for watch only (that includes pause time as the sensors are still on - so if during a 2 hour activity you had 30 minutes of pause it was 2:30 of battery life, not just the 2 hours it was recording for). Those of course are estimates and best case scenario and are impacted by usage (using back-light, switching screens, etc.) and environmental conditions (overcast skies, tree cover, tall buildings, etc.). If you have night mode or the back-light on that is going to impact it greatly. I have found that they are pretty accurate estimates and my usage and testing has pretty well matched them. Bear in mind that the battery gauge is a rough estimate at best and I have gone many hours when it indicates that it was almost empty.