Now you mention it, my iPod Touch keeps telling me to recharge the battery. When I connect it up, it often has a retained charge of almost 50%.
My iPad Air 2 and iPhone 6s updated to iOS 12.4 okay and haven't given me grief. I do feel the phone has become somewhat power-hungry since ~11 though.
I'm out of Apple's clutches at the moment, but treat Android updates with equal trepidation. if iPhones had expandable memory, I might consider switching back, but the higher storage capacity ones are just too expensive.