Have multiple backups is good and checking usability of backups is good too.
If a wallet on our device is still usable but our backups were damaged and can not be used when we check backups, we can make new backups to replace old ones. If we think backups can be used forever and don't check them regularly, when we need backups for recovery, we can have nightmare.
Multiple backups are good to protect our funds when our device is broken and one of backups is damaged too.
Right, and you should be verifying each copy that you make of a backup every time, by importing the private key or seed into a offline client, and verifying everything matches up. Not enough users do that, and tend to neglect verifying because it takes time. However, it could potentially save you from losing your Bitcoin.
I wish there was a way of teaching newcomers this, without it being an hindrance to them. Probably, isn't a easy way of doing that though.