I had a similar experience with a Samsung Galaxy S4, which would run out of battery life in under 5 hours on any given day, and which was dropped for major upda

I had a similar experience with a Samsung Galaxy S4, which would run out of battery life in under 5 hours on any given day, and which was dropped for major updates after two versions. Switching to Cyanogenmod, even the nightly version extended battery life to ~9 hours, and greatly improved performance. It also allowed access to the next version of Android, and native skinning and easy customization (with a literal toggle in the dev settings for root). In short, I highly recommend upgrading any old hardware you have to Lineage OS (Cyanogenmod continued).