There's an idea going around that there's not a whole lot of improvement in smart phones these days. If there isn't much improvement in the new phones there isn't much reason to upgrade until yours breaks.
In such a market repairability and durability seem like they become much more important than they used to be. I haven't seen any evidence of that currently but I sure would like to. The only phones that are easy to take apart and swap parts on are budget phones made of plastic. You know, I have nothing against plastic. The problem with budget phones, by and large, are the processors and screens, Etc. At the very least, we all know that batteries wear out. Being able to put in a new battery seems like such an obvious feature if you're going to use your phone for more than a year.
Peak smartphone refers to the number of shipments per year.