If main NavStick is working good, there is no need to download the updates twice for your second NavStick. This will only result in more unnecessary wear and tear on the backup NavStick. And many times the backup NavStick is set inactive in our system due to this.
For backup purposes, please use the NavSync backup function (accessed via "Settings" down in the right corner) instead, and perform backup regularly, at least every 14 days. (See attached screenshot)
The backup Navstick should be stored in a safe location, and in the event that your main NavStick should fail, you can contact us and we will guide you to restore the latest backup files to the backup NavStick.