My phone once lost a whole month of notes. It decided to sync with the void. I've had reminders for farrier appointments just vanish. Trusting it feels like trusting a squirrel to guard your bird feeder. It works until it very much doesn't.
Actually, it's not about trusting the phone itself. The real risk is relying on a single app without a backup. A quick export to a text file every so often solves the whole problem.