Upgrading the battery on my iPhone 12 Pro has been a fucking revelation. I just don't run out of battery any more. I'm sure Apple was telling me it was only 20% degraded or something too, but I would strongly, strongly recommend this if thinking about battery life is currently an issue for you.

That could be a factor for sure, but this iOS upgrade basically broke mu iPhone as switching between apps got noticeably slower and sometimes the UI gets stuck for a second or two especially when switching between the camera and other apps. I'm so sorry I gave in and installed it.