What to do if there's an update for my child theme?
We don't normally update our child themes unless we (or our users) find an error or bug; or if ET updates Divi in such a way that it causes some error in our child themes. For example, one time we updated a child theme to fix an error in the demo content import, if a user didn't have any problems with that then there's no need to update. If you do update, remember to back up your edited files and then replace the overwritten ones.
If you made any edits in the CSS and/or PHP files you should save backups of those that you did modify before updating a child theme, because they will be overwritten in the event of a child theme update. This does not happen when the parent theme updates.