I thought that I would share my experience with all. First thing is that Marshmallow is a problematic update.
I had bought a new battery from Amazon back in May because I was getting less life after the Lollipop update. I will own my phone two years at the end of October. After all, a prime benefit of this phone is that it has a replaceable battery.
I was plagued by random restarts and very bad battery life after Marshmallow. I factory reset the phone and went into safe mode, per the Verizon CS. I still had the random restarts and they shipped me a new phone. Guess what, I rebuilt the new phone and still had problems with the battery. Turns out that the battery, which I bought on Amazon was either some counterfeit or the Amazon seller had shipped me a "recycled" battery. It was a battery problem and did not the refurb phone.
With the brand new "real" battery, I am back to about two days. With my original battery, I was just making it to the end of the day. In the past I was able to run location all the time, but I am now turning it off until needed. You may also want to use some of the automation tools, such as Automate, MacroDroid, or Automate to switch off wireless, etc as you travel around.
I hope that this helps.
I am experiencing the same battery issue as you have listed, and purchased the new Samsung battery from Amazon for $9 which is worthless. I will look for a different battery at Staples. How do you know if it's a valid Samsung battery?
ONLY authenticated batteries work well as in ordered from Samsung, i tried knockoffs too, but they were no good. got one from them worked well. u get wat u pay for.