Its stating the blindingly obvious, but phones and tablets break, get dropped in puddles, decide to stop working for no apparent reason. So while they’re very useful and generally reliable you still need a backup.
As Nikki from CoDA says (I summarise);
Keep lots of backups, keep them on different media and don;t keep them all in one place.
I’d add one further tip, which is to check from time to time that you can actually read your backups – you’d be amazed how often a crisis occurs and its only then that people discover the backup wasn’t working properly.
Archaeo-Pad will nag you make a backup, the default setting is every 2 days, if you want to live dangerously will take to the Preferences page where you can extend the interval.
I’d recommend leaving the setting alone and sending a backup to yourself by email at least once a day, just make it the last thing you do before cleaning off your trowel! And make a separate copy to the cloud or to a hard drive as well.