Hey guys! A brand new lumia 950 owner here (Been using it for a week now. Won the phone from the recent giveaway xD). It's an International Unlocked, Dual-Sim version 950 from the US (I'm from Malaysia). Just wanna share something to all of you regarding my experience with the 950's battery and overall performance.
Anyway, as most of the people here, I too faced the battery drain problem. Battery went down 40% with light usage in about 45 minutes (that's 1% discharge per minute!). What I did to solve the problem temporarily was to update the phone to the latest Insider build (RS2 build 14915.100 from TH2 build 10586) WITHOUT updating the apps (there was a firmware update as well), then performed a hard reset WITH NO BACKUP. Then I updated all the app, registered my mail accounts (set to sync as items arrive), set up WhatsApp, Messenger, Instagram, Facebook, Twitter, OneFootball, AppRaisin, MangaBlaze (apps that I would allow to run on background normally). Location set to off, no 'Hey Cortana', Iris Scanner is on, no glance screen, and Find My Phone set to On, with the frequent option off.
With all of these settings, the battery life was sub-par, about the same as my previous 830. A full charge with my normal usage (receive and reply about 20-40 WhatsApp messages, receive 2-4 e-mails, casual Instagram/FB/Twitter/OneFootball/Win Central/AppRaisin browsing), and my phone lasted from about 7am until 3pm (phone is at 5% by 3pm). Granted, all the background apps were running as well, and that my casual browsing for Instagram alone is about 5 minutes average. So if I assume I used those respective apps I mentioned above for 5 minutes each, and browsed it around 3 session during the entire 7am-3pm observation, that means I had been actively using the phone for 2 hours and 15 minutes. I would say it's quite a medium-heavy use for me (for a more heavy use, I'd watch YouTube vids or play my music via earphones, along with doing all of the stuff above).
Also of note, my Iris Scan was blazing fast for the first few times I've used it, but gradually it got slower and slower. Also, the camera is a bit bugged, in a sense that the resulting pictures weren't nice, not up to par as what I'd seen from other users/reviewers result. It was way oversharpened, colours not vivid at all, and a bit blurry I might say (not sure how to explain the contradiction where it's sharpened yet blurry. I guess it's like some part of the pictures were oversharpened, and the other part were blurry. And no, this is not a bokeh effect as I'm taking a picture of my classroom's whiteboard). General performance while navigating through the phone were alright, I guess.
Still, I'm not satisfied with my 950's battery life and performance. As per suggested somewhere on the Internet, I did a WDRT to my phone, updated to 14915 again and then updated my apps afterwards, set up all my account the same way. This time, however, I set my mail to sync 30 minutes, disabled background activity for Instagram. My battery lasted from 12.15am, 100% fully charged, until about 7.45pm. Same usage as above except that I actually played music via earphone for about an hour as well as streaming a 1080p video for 5 minutes via cellular data. That's 19 hours 30 minutes of battery life. I'm not sure about you, but with heavy usage my phone actually lasted me throughout my day of heavy use ^_^
Now, I plan to sync my e-mails hourly instead of every 30 minutes, as well as turning off the save my location under Find My Phone. Hopefully this would gain more usage out of my phone! ^_^
P/S: Most of the time, my phone was connected to WiFi. I'm guessing that using cellular data / mobile data would drain the battery faster, and I estimate my phone to last about 14 hours with data constantly on. Just my prediction tho.
tl;dr: WDRT for better battery life, as well as turning off some background apps and sync e-mails every 30 minutes.