Battery life

I'm only getting about 3.5 days of battery life on my Fitbit Air. The only setting I've changed since I got it was switching which wrist I wear it on. Other than that, everything is the same.

From what I've read, the battery is supposed to last significantly longer, so I'm not sure why I'm only getting about half of the advertised battery life.

Has anyone else experienced this? Any settings or features I should check that might be draining the battery?