I got my S7 in April. The battery has been rock solid, I mean amazing. I went away 3 weeks ago to Lake Tahoe. Not the best cell reception for a few reason... tower coverage and when it gets heavily populated, especially on the weekends cell towers are getting hit.
Anyhow - its odd, since I have returned my battery is getting drained much faster and I am seeing Cell stand by as main culprit. . Also, there are a few dead spots near my house if you have verizon. I never get signal. Since returning now get 4g in those dead spots. I know Verizon has not increased cell coverage as my wife is using note 4 and she still gets no signal, likewise with friends using Verizon. It might sound odd, but its as if the week in Lake Tahoe where phone struggled for signal has tweaked my phone. It sucks... my battery would get me a full day and half on full charge before my trip now I am not getting through the day.
Might be time to wipe the phone and rebuild