Re: you made a poor decision on phone
Why should you buy a phone every 2 years? As that is pretty much it's usable lifespan. By the time 2 years is up, you have run out of support credits. Now hundreds of thousands of people were prepared to pay an extra couple of hundred quid for the same phone, then there might be enough credits in the support kitty to provide longer support.
Its basic economics, you get what you pay for. The Samsung S4 is an ancient phone and clearly not capable of security backports without massive development and test resources.
If you wonder why Lineage is better as stable as real Android it's because it cheapskates on both Dev be testing and rely on crowdsource