How are you getting 7 hours of SOT? I've had my phone off the charger since 8:30 and I'm down to 20% with only 2 hours of SOT and Bluetooth running.
Wow, I'm not doing anything special besides changing the sync times for my 5 emails (3 gmail, 2 regular email) accounts....ie, I turned OFF sync and then just pull emails. I have a separate corporate phone which receives my work emails so i don't need to have push emails on my personal Note 5. I use bluetooth all day as i'm paired with my Moto 360 2nd Gen watch. I'm on AT&T 4G LTE all day at work and then connect to my home wifi from 7pm till i fall asleep around 1am.
i don't use any of the app disabler stuff mentioned here...i don't use any battery monitor besides whatever comes on the phone. i have NOT disabled any of the ANT services like i had to with my previous S6.
I think if you're only getting 3 hours of SOT, you should probably try to exchange that. you should be getting at least 13 hours of total standby time/per day and at least 5 hours of SOT with heavy use.
I have turned off the setting so that Wifi turns off while phone is asleep. I use a dark theme and dark wallpaper.