How often you should back up the company file depends on whether the file is online or not:
If you work online, you don’t need to back up your company file each session. However, you should make a backup of your online file before starting a task that will result in significant changes to your file, such as closing a financial year or importing data. You would also make a backup if you want to archive a copy of the file as at a point in time, such as month-end.
If your file is not online, you should be backing up your company file regularly. Having a recent backup is a security measure that will help minimise the rework required if the company file you use is lost, stolen or damaged.
You should store your backups on removable media, such as a USB drive, and keep the backup offsite.
If you don’t want to be reminded
To switch off the reminder, select the Don’t show again option. To switch this preference back on, go to the Setup menu > Preferences > Security tab > select the option Prompt for Data Backup When Closing.