I read your post but I don't see how it answers the question. You just say there is a problem with hidden addresses.
You DO NOT need to back up your wallet after each tx (the more technical details were to try and explain that you do still need to make regular backups).
If you have a lot of tx's occurring regularly then you might consider increasing the pool size.
How do I do that?
There is a setting you can put into bitcoin.conf (although for most average usage it should not be necessary to change this).
If you want to just have a *single* backup then you will need to use a client that creates a "deterministic" wallet (the Satoshi client does not have this capability yet).