I am wondering how to know if the keys for the addresses that are used to receive the "change" from the transactions are included in my backups? I am concerned that even though I may never create "new" addresses by clicking "new address" in the "receive coins" window, that I may end up sending a transaction and having the change go to an address that is not in my backups, and then suffer hardware failure and lost funds as a result.

I am trying to put my mind at ease without having to make new backups after every single transaction, or sweep funds to an address that I know is in the backups after every single transaction. Any information on the matter would be appreciated.