I am really liking the Extreme Battery Saver. If I go through the whole day with it turned on about 80% of the time, I still have 75-80% battery left at the end of a long day. I like that it disables all apps but essential ones (phone, text, camera, and I set Outlook--for email--as an essential app too). It grays out the icons for all apps that are turned off, but if you want to use one, you just open it as normal and it asks you if you want to temporarily turn it on, and then it turns it back off after a few minutes. This is nice so you don't have to keep turning extreme battery saver off and on when you need to quickly use an app.
I put the battery saver in my top shortcuts tray, so I can just swipe down from the top to quickly enable/disable battery saver and data saver, then just click the notification to turn on Extreme battery saver. Not only does this save A LOT of battery, but it also keeps unwanted apps from constantly doing stuff in the background.
I also turned on the "Turn Over Phone" to enter DND mode which I love having.
The P5 is no slouch on battery. Even without battery saver enabled, I get through a whole day and still have 55-60% battery left, but with Extreme it's about 20% more battery. This is easily a 2-day phone between charges. Almost reminds me of my old BlackBerry days when I could go 3 days easy between charges.
One last bit... I have only plugged into this phone's USB-C port once, and that was when I set it up the phone out of the box and did my data transfer. The rest of the time it's been charged on the Google wireless charging stand, and I've had the phone a month now.