I agree with a lot of what you say here. The only factor I can see that could potentially cut the life short of a device or ruin the user experience is the updates. Up until 4 weeks ago I couldn’t fault my 6S. Battery life was brilliant, the navigation was smooth between apps etc. Now after 4 iOS 11 updates my phone is still into lower power mode by 2.30pm most days. The animations freeze often too. Today I was trying to take a photo of my two little girls and we all know you have to be quick with kids. The bloody camera froze up! Repeatedly pressing the home button in panic not to miss the opportunity and I get the Apple logo. I actually threw the phone at that point lol.
I do wonder how many more updates my phone will take and it’s just over a year old. It’s pretty bad form by Apple and sadly mine isn’t an isolated case.
My 7 Plus has lower performance,delays and battery life issues on iOS 11 as well. It's just not a good release. Battery life especially has taken a nosedive.