Y'all realize that this is apples and oranges right? If I'm tethering to my laptop, brightness all the way up, 1 bar of reception, streaming something to my Apple TV, and playing some heavy game my minutes usage are going to be a lot less than someone who has brightness all the way down, only using Kindle to read a book they downloaded already, sitting next to a WiFi Router with solid cell reception will have far more minutes used.
Just putting that out there. I am usually a light cellphone user and can get 3-5 days out of a single charge on my 8+. My wife will go through a charge on her 8+ in 3/4th a day because she uses social media, talks to her friends a lot, watches videos, snapchat, Facebook, etc...