If you create a new wallet.dat, encrypt it, back it up, getnewaddress and send funds to it, does the back up of the wallet.dat also have the new address? Does getnewaddress actually create a new address or just assign one? Is that what the keypool size is?
You don't have to back it up after every new address generation.
But you have to after importprivkey because it's a new privkey added to your wallet.
Doesn't each new generated public key have a new private key associated with it? So I you don't backup the wallet, you won't have the newly generated key pairs . Would be odd that it stored a bunch of keys just in case.
I did not know how that works either. Here it says "The keypool parameter just sets how many extra keys the client creates when it needs to create keys."
http://bitcoin.stackexchange.com/questions/770/what-does-keypool-1-dothe wiki does not give explicit information about this
https://en.bitcoin.it/wiki/Key_poolso YES, executing getnewaddress means you need a new backup
No, you don't. If you start your old backup wallet you will have all coins sent to you at your new addresses.
What you won't have is just addresses in your book.
Edit: You missed that post in your link:
"With keypool of 100 (the default) you could make 100 new addresses (via new transactions) and the backup would still be valid." DeathAndTaxes Nov 5 '11
Satoshi
https://bitcointalk.org/index.php?topic=1414.0