I've had my S4 for 1.5 years and I have zero issue with the battery life personally. I keep all things completely turned off that I don't use. For instance, all Samsung features (read mode, multi window, etc.) It's also been recommended to keep your screen NOT set to auto brightness, as the constant change kills battery percentage. Other things... Data, bluetooth, wifi are all turned off until I need them. I'm not wholly dependent on my phone, so this is an option for me.
Also, a lot of preinstalled apps run constantly in the background, so if you're not rooted, you can go through the Application Manager in the settings and uninstall any unused applications to fix this as well.
There could be many more contributing factors.
Like if you have email set up on your phone via the Email app (not Gmail) and it is set to Sync constantly as opposed to a longer time frame.
What to you use on your phone most frequently?
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