Bitcoin Forum

I'd like to verify the following assumption is correct:

Lets say today I have 10 addresses in my wallet, each holding 0.1 BTC and I backup wallet.dat to a safe location.
Tomorrow I'll add another address that holds 5 BTC, but I don't make a new backup. A few hours later, my hard drive crashes and I need to restore the backup of the older wallet.

I will have lost the amount of BTC from the address that has not been backuped, 5BTC but I will be able to recover the 1 BTC from the other 10 addresses?
In other words, you will only need to make a new backup in case a new address has been assigned that has funds on them?

It depends on the wallet-software.

Bitcoin-qt generates addresses in batches of 100. It will use an address from the pool every time you request a new receiving-address and every time you send coins (for the change-address). So you should backup your wallet-file every 100 (receiving-addresses requested + transactions sent).

Other wallets can have different methods to generate address. For example, Electrum generates addresses deterministically using the initial passphrase. No backups beyond the first are needed here.

I'm using Bitcoin-qt (v0.8.6-beta).

There are 12 receive addresses in this wallet, and 4 sent transactions.
So I should be good for another 84 combined (receive addresses+ sent transactions) before making a new backup?

Correct.

Of course it never hurts to back up more frequently.