I can make the battery last all day.
1) I can remember my ADR and FP times in my head - but I do write them on a Post-It the night before in my room - and put the post-it on my credit card that is going with me to the park. That way - I can look them up there - instead of the phone.
2) I do take pictures with my phone throughout the day - but I really, really make few, if any videos. And if I do - they are short. And I might post a photo or two to Fb, or email one - but I save any large uploads to other sites until the end of the day.
3) I don't check my phone all day long. I try to avoid the constant email checking, social media updates. This helps me stay in the moment at WDW, too. On occasion - something for work is urgent - and I have to keep doing stuff - but then I take fewer pictures and rely more on the post-it, avoid videos, etc.
4) I've done mobile order once - when I already knew what I wanted. But frankly - if I didn't know - I'd just wait in the line and browse the menu they hand out at QS places instead.
5) I have successfully added a 4th and 5th FP on my phone. But - I also know where the kiosks are - and I have used those. Especially later in the day - they rarely have lines.
6) One day - I was pretty low (single digits percent battery charge) relatively early in the day. I switched to airplane mode - and avoided using it unless absolutely necessary - and still managed to get a good photo in the park on my way out as I had a bit of charge left.
7) And frankly - I use a paper Times Guide instead of the app for showtimes - it's just faster than the app.