I never experienced a random shutdown on my old iPhone despite not allowing the software update for years. Finally, when I did update the phone, everything was

I never experienced a random shutdown on my old iPhone despite not allowing the software update for years. Finally, when I did update the phone, everything was noticeably slower, instantly, so that sounds more like good PR management than actual consumer-minded thinking to me. Yes, devices get old and batteries get old, but my understanding is that this happens even if you replace the battery with a new one, which would negate this argument.