Yea, it's pretty good I can get ~4 hours of straight video (I bet 4k wouldn't but that much less since it does use hardware encoding). I was more commenting on that was the only time I seriously used the phone. I use to read on the phone too before I got a much better e-reader. Now I just use it to read a synced book if I'm waiting in line by myself.
It's interesting being out at a bar and looking around and seeing how many people just constantly look at their pocket machines. I only constantly check mine if I'm waiting for friends to show up so I don't miss a text. But often I'll be at a party for hours and in a conversation say, "oh let me show you a picture I took ... oh wait, my phone is in my car .. or out of battery .. or in my car and out of battery"