I highly recommend doing a factory reset in situations like this. I know most people don't like to and it can be a hassle but I do it almost monthly and it's really not a big deal to me. Yes, it will take a couple days to set all your apps back up as you use them but I find I end up trimming down apps and sometimes changing how my phone is setup to making things leaner and more efficient.
Anyway, you might want to consider a factory reset, it tends to cure most issues with major version updates. I'm getting great battery life especially now a couple weeks into Pie.
Doing a factory reset every month or couple of months is a really good idea - thanks for sharing that too! It'd be worth it to better customize your phone and to make it more efficient.