To add what's already been mentioned. Themes that rely on widgets are heavy battery drainers. Also Activator, Zephyr, SBSettings, IntelliScreenX are also known to drain battery juice quicker.
Some tips to improve battery life:
-Location Services > System Services > Setting Time Zone - OFF
-Location Based iAds - OFF
-Weather - Local Weather > OFF
-Notification Center > Stocks > OFF
-Bluetooth + WiFi > OFF (when not in use)
-General > About > Diagnostics & Usage > Don’t Send > ON
-General > Restrictions > Ping > OFF
-General > Spotlight Search > Mail - OFF, Messages - OFF
* close background apps (I use an app called "WeeKillBackground Pro" to accomplish this) *
Also MANUALLY adjust Brightness Display (depending on time + current lighting condition) and turn OFF "Auto Brightness."
Last but not least.....ignore the "PMS troll" aka heyyitzmelissa
