Knowing the issues with fixed in batteries these day, I purchased myself an LG G3, one of the few good smartphones with a replaceable battery. The idea is that once it goes bad, it'll be a simple switch.
The problem nowadays is that it's almost impossible to get an original battery. On Amazon, everything is a fake. In stores, the battery does not exist anymore or is super expensive. It seems LG doesn't care, maybe they speculate people will just buy new phones.
In a way, my approach to have replaceable batteries failed.