[gruez]

> Early Android devices had removable batteries and most of the popular ones had custom ROMs that extended support for way beyond OEM updates.

how long is "way beyond OEM updates"? one year? two years? three years? five years? The main problem is that third party roms can only update so much. Without OEM support, you're not going to be getting updates for the proprietary bits of your phone. This includes blobs, baseband, and even the kernel (technically it's open source, but all android phones run off a customized kernel that's specific to that SoC. When that SOC gets EOLed, the updates stop coming).