I've had the Gorilla Gadgets 4500 mAH extended battery for about 6 months now. It's worked very well for me up until the last month. I hardly get through the day and the battery drains so quickly even while on standby. I've recently checked the battery usage and it usually says that 70-80% of my battery is being used up by my screen. Just yesterday, it said that I used 2 hours of screen time, which consumed 70% of my battery. Any reason for this happening? I should be able to get much more screen time with my phone, and it shouldn't drain as much while on standby. Not sure why it started happening all of a sudden.
Hello OSU.
Well, most often when a sudden change in resource drain is seen, it'll match up with some change the user has made, either in usage or in addition of an app/widget or in configuration of the system or one of the apps/widgets, given that the battery stats are correct as displayed (clear those in the Application Manager and reboot to test that

).
Having said that, some 3rd party extended batteries do seem to dry up in performance rather quickly. One year is supposed to be the average life of a battery for these smart phones, extended or stock. 6 Months seems a bit on the low quality side, unless, as mentioned, there's a configuration or app/widget or usage reason.
Also, have you changed location? If so and it's farther from a tower/signal source, your device may be draining resources in an effort to keep polling for a strong signal.