My wife had a phone replaced off Apple about 6 months back because it was shutting down for no reason about 40% battery life. She’s recently upgraded from 10.x to latest version. She’s noticed an actual decrease in performance to the point where she’s nearly punching the phone. It just locks up for no reason. I’d like to blame this on the battery or age of the phone but I can’t. It is an iPhone 6 but it is only half…
Was her replacement phone a refurbished or new unit? Either way, she can probably get a brand new battery just by taking it in to the Apple Store. Also, battery age isn't actually time based, it's cycle based. If your wife uses her phone so heavily that she has to recharge it multiple times a day, she's putting more cycles on the battery. Still should last more than 6 months though.
I’m going to install the app to check what the CPU is running at.
It’s still ridiculous that she was running 10.x fine, she only updated because someone sent her some emojis that her phone didn’t understand and now is it’s running like crap