As far as power management is concerned, I consider myself pretty well versed...
There is nothing wrong with your battery performance. You have 4 1/2 hours of SOT over 45 hours. That is, by any account, quite good. If you have an S6, it is EXTREMELY good.....Even if you had the Edge+, that's good. there are people with the S6E who don't manage that much over the course of less than a day.
What are your expectations?
One thing to keep in mind.... SOT and total charge time are inversely related. If I took mine off the charger and just went hell bent for glory, I could get 7+ hours of SOT, but I'd have to charge it in in 10 or so hours.... If I wanted to change once a day, I could do up to 6ish.... If I wanted to push it to once every two days... 4 hours or so. etc.. If I just popped it my table and didn't touch it, I could go a week with next to no SOT.
My active drain is about 12% to 13% an hour, and my average idle drain is about 1%... some combination of those two numbers will dictate how long I go between charges and how much SOT I can expect during that time.