I have an old IPhone 7 Plus that I use for utility (target camera for handgun laser pulse cartridge training, audio recording, etc) and have seen zero issues with the battery life after the upgrade. However this phone is only connected to Wi-Fi, perhaps there’s something different for phones connected to cellular.
Also, zero issues on my iPad 10.5 pro which only gets used for reading books.
Needless to say, no issues with my 2020 iPad Pro and iPhone 12 Pro. And I recently got 26 hours from my Apple Watch 6, with 16% power left. (I had forgotten to swap to my 5 when I went to bed the other day).