Just got the 6 Plus today and it came with 80% out of box around 12pm.
I have used it HEAVILY since then
Truth be told, I'm trying to drain the battery so I can cycle it through to 100%
I used GPS navigation for a solid hour. I've been downloading and using all my new apps. I've been taking pictures and videos just to see how they look. I've been surfing the web and social media sites. I've been texting heavily all day and night because I had dinner plans with a bunch of people tonight.
I know all of that sounds pretty normal, but I honestly haven't even put my phone down. My wife got annoyed earlier lol
Anyway, it's now 11pm and I'm still at 10%... So I've used about 70% battery after 11 hours of HEAVY usage.
Based on this first run-through, I have no doubt in my mind I'll be able to get 2 days of average use out of this phone... and I should never have to worry about my phone dying within one day.