Please confirm my understanding of backup

[AliceWonder]

Talking about the reference qt client in Linux (I'm using the rpm from http://linux.ringingliberty.com/bitcoin/ ).

My understanding - just by launching the application for the first time, 100 reserve key pairs are created.
Every time I ask for a new public key, one from the reserve is used and new one is created to add to the reserve pool.

So if I backup my wallet, what gets backed up is all private keys including those I haven't used yet in the pool.

Thus on a virgin wallet, if I create a backup, receive 90 payments to 90 addresses, hard drives fries before making another backup, I can use my backup in new wallet - it will find the coins I have from the blockchain.

But if I receive 110 payments to 110 addresses, some of those address private keys are not in that backup so those coins are lost forever.

Hence one should backup often enough that they are not receiving coins to a key not in pool at last backup, but backup doesn't need to be done daily unless you receive a lot of payments in a day.

Is that understanding correct?

[orymh]

You have it exactly right: Back up about as frequently as you create new addresses.

[jklp]

Is that understanding correct?

Sounds right to me.  Or use an online wallet and they'll "back up" your coins for you. 

[AliceWonder]

Is that understanding correct?

Sounds right to me.  Or use an online wallet and they'll "back up" your coins for you. 

Too many on-line wallets have been hacked or were scams for me, I have trouble trusting them.

[Maged]

Also remember that you usually use one of the keys from the key pool as a "change" address every time that you send bitcoins.