I have my iPad4 automatically backing up to iCloud at night when charging and connected to Wi-Fi. Everything works fine and the backup size is 1.6Gb. With this auto backup does it mean that everytime it backs up automatically that it backs up everything again or just what has changed since the last backup. I don't like the idea that the backup is using 1.6Gb of my monthly allowance everytime it backs up. That would mean anything up to 48Gb being used if it backed up every day for 30 days of the month. If this is the case then I will be turning off this backup as I only have 25Gb monthly allowance.