This is a good, safe, butt-covering thing to do before running an iOS software update, or before you migrate to a new device. iCloud backups are an enormous convenience, but I subscribe to Murphy’s Law, as well as the 3-2-1 Rule of Backups, so I like to maintain a backup of my iPhones and iPads in iTunes on one of my Macs:
First and always, make sure you have good backups of your Mac.
Then, clean out your old iOS backups in iTunes:
- Click on the iTunes menu, and go to Preferences…
- Click on Devices.
- In the list of Device Backups, with the dates, look for duplicate backups of your devices. Note the most recent backup, and leave it alone.
- Now click on each of the other backups, and below, click the button called Delete Backup.
- Do that for each duplicate backup, leaving only the most recent ones.
- Hit OK.
iTunes will take a bit of time to delete those files. You may see the rainbow beach ball.
Now, near the top of the iTunes window, under the search box, click on your iPhone or iPad. On the main Summary page, make sure that Encrypt iPhone Backups is turned on. If it’s not, click the checkbox, and enter a password. (As long as you choose Remember Password in Keychain, you can pick anything.)
iTunes will now run a full backup of your iOS device, including passwords for your sync accounts and wifi networks.
jjmarcus tech solutions 
Each of our macs have a single backup. Our iPhone’s backup before each and every sync. I think we are using the default settings – is this really needed?
I was careful not to say, “You must do this.” But, even though it’s much better now, I had enough disappointment in Apple’s mechanism last year, and it’s still not transparent enough, that I want to be sure I have a clean, pristine backup of the phone before I update.