When facing a problem with a battery, we often think that it is a hardware issue. Of course it can be one of the causes, but software also has it’s role to play. As you know, closing your apps when you don’t use them, turning off the useless notifications, turning off the usage of the GPS are the first things to do.
If you still have a battery drain, maybe you should also check which applications are using the most your battery. With iOS 8, this is now possible. Go to your settings under General > Usage > Battery Usage and find out which apps are using you battery. You might be surprised. Maybe apps you don’t use that much are the ones consuming the most battery for you. Just have a look!
You might also want to check this page on Apple’s website: https://www.apple.com/batteries/maximizing-performance/