Firmware Update Kindle touch (4th gen) poor battery life after 5.3.7.3 update

[Sehn82]

After the mandatory update, I've noticed my Kindle touch's battery life has taken a nosedive. Previously it could last weeks and now it barely lasts 48 hours on standby.

I put it off as regular battery degradation since the device is pretty old anyway but after getting a new battery recently and having it installed, the issue still persists.

Tried reset to factory defaults sans books to see how it fares but it was still the same.

Could it possibly be due to the firmware? 5.3.7.3 is the latest one and it doesnt' look like Amazon will be updating an EOL device's firmware.

Any others experiencing the same situation? If it's a firmware issue i'm wondering if somehow using an alternate firmware might help.