iPhone 5S poor battery life with 8.3

Hello,

I'm using iPhone 5S 16 GB for past 8 months. It's currently running on version 8.3. When connected to 3G (or 2G sometimes) the battery starts draining like anything. With 3G usage the mobile lasts for hardly 4 hours in 3G and 5 hours in Wi-Fi. I even tried visiting the istores twice and resulted with no issues with the battery.

Following troubleshoots were performed in iStores:

1. Upgraded the OS to 8.1 for better performance.

2. Battery diagnosis performed and no issues found.

As per specifications, it's not up to the mark. Can any one suggest me what to do to prevent this or is my battery is defective? Is this a normal issue for all iPhone 5s Your suggestions are much appreciated. Thanks in advance 🙂.