I too have noticed a small decline in my iPhone 5 battery capacity. While I originally attributed it to going from Wifi to LTE, this quickly became debunked as spending the entire day on Wifi I still have a low battery. As of late my phone seems to have adjusted and my battery life is back to some-what normal. A few things I may suggest...
-Lower screen brightness to 50% or lower
-Take your phone OFF Wifi whenever you're leaving a WiFi-designated-zone
-Put your phone to sleep - thus saving battery power
-Turn off some of the notification settings for apps you may not need to be notified about
-Turn your email account(s) to push for new email only when you open the Mail App (manually)
-Stop using your phone so much
Hope that helps those that are still have battery issues.
PS: And as AngryCPA stated; about once a month charge your phone full, then use it until it literally dies. This conditions the battery and keeps its capacity near full.