How long does the battery last on the watch?
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.