Given the very apparent weight difference it can also be a matter of portability. The Mini is definitely easier to be "mobile" with. (Though not if the iPad Air is being considered, though that's at a steeper cost.)
Everybody buys online: this is just acknowledging brick and mortar in a bookstore environment isn't cutting it. They've retained educational discounts and with online customization: the way to go. No "doom" required.
On some previous iOS upgrades I noticed settings changed: so you might also look at things like location services: constantly running the gps chip with full power etc. being a battery drainer. Or other such settings. An app being stuck "on" for whatever reason will draw power. Or WiFi or Bluetooth and such. fwiw my 5s is not exhibiting that. Usage: 1 hr 21 mins. standby 8 hours, battery 85%Location services on, WiFi on, BT on, pretty much everything "on"...
There's a certain logic to that isn't there?: work the problem to a solution, whether that be getting the device replaced (which few seem to bother trying) or simply move on.... or read the user guide.... ("Why can't I just!")
Upgrade to their product line. And someone has to buy the last one: if it's years into a product's life getting annoyed is silly: the writing is always on the wall as the calendar moves forward. A purchase should be made because the device does what it wanted. That being the case nothing changes when it's supplanted by something that does other things.