Hmm. My $170 phone from the middle of 2014 is still working perfectly and shows no signs of being "deprecated". Every application I use gets frequent updates, including the browser. I don't have to worry about targeted attacks (as I am not a billionaire/movie star/CEO of a large company/whatever), and a new shiny iPhone won't help with those anyway. µBlock Origin (with JS disabled on most sites) protects me from everything else.