Welcome to Over50sForum! The site for people over 50 to chat, make friends, discuss, share, and generally be part of something that's fun and friendly :)
Don't know about the inns and outs, but, it's really annoying there is no audible "Beep", at say 5 minute intervals, to warn folks, who are not constantly checking the screen, that the battery is about to fail.
You can get batteries replaced quite cheaply on iPhones - they do a good job, too. It's probably not worth it if you're phone is quite old (iPhone 4 or 4s).
One thing I do like about iPhones is that they all get upgrades at the same time whereas on Android you're at the whim of manufacturers.