iPhone 16 pro max here got on release date too.
I don’t know how you guys are going through your battery, I charge it, as soon as it gets to 100% I take it off so normally it’s at 9pm-1am when and if I wake up in the middle of the night. From then to 1:15pm my phone is at 91%. I go to work and don’t use it much listen to music on the way to work, text people etc. After work obviously I will be on it more but even then from 1:15-9:15pm it goes to 63%. Some days I don’t even charge it going to bed I will wake up and charge it when I’m getting ready for work. From the iPhone 11 Pro Max to the 16 I would say this is a huge upgrade for me usually my 11 would have died by 4pm.
I would also go into settings >battery and see what background apps are running and the top ones I go and turn off background app refresh and that tends to help or delete to app if I don’t use it. Like for example I had temu on there (I know don’t hate) but I saw it was on in the background even when I didn’t go into it at all so I deleted the app. So much better now. I would also go to Apple and just check and see there has been times where I’ve gotten a product and the battery expanded during elevation changes etc.