Re: Choice
You don't have to switch if you don't want to - as long as you don't "need" the new features (such as they are).
I recently bought a second-hand (64GB) 6S from Mazuma Mobile, which although in "Very Good" spec looks almost new to me - with a 12-month guarantee.
When/if my 6S (with new £25 battery) conks out, I'll look at replacing it with a second-hand (or Refurb/Renew) phone from them (or a similar provider) or pick one up from the hight street shops that seem to have loads of decent corporate offloads for reasonable money.
With the current high-profile campaigns against single-use plastics etc., I am surprised that this route is not gaining a higher profile or chosen by more (of those who care about it...) due to the energy-dense production processes involved in these devices (whether Apple/Android or not).