When I have to backup wallet.dat

[Wed]

Hello together,
I'm a little bit confused.
When do I have to backup my wallet.dat?
Just one time or always after getting new transactions?
Is it possible to get all CURRENT bitcoins back with an old backup?
What's the difference between an old backup and an actual backup?
Would be nice if someone could explain it to me.
Thanks

[Graet]

Hello together,
I'm a little bit confused.
When do I have to backup my wallet.dat?
Just one time or always after getting new transactions?
Is it possible to get all CURRENT bitcoins back with an old backup?
What's the difference between an old backup and an actual backup?
Would be nice if someone could explain it to me.
Thanks

The default client pre-generates 100keys best to back up every 100TXN or less
if you do lots and lots of transactions you can raise the size of the keypool, but still best to backup before that number of transactions completed

the problem is, new change addresses that may not appear in backups that are too old

[Wed]

Okay in short, backup it before reaching 100 transactions. For example 95, 195, 295, and so on. (in case of using default settings with default wallet)
Am I right?

[DannyHamilton]

The first question is "Which wallet are you using?"  Each wallet operates a bit differently from the others, so useful advice needs to be wallet specific.

The advice that you received from Graet assumes that you are using Bitcoin-Qt.

Note, that it would be wise to have multiple backups in case one turns out to be bad, damaged, or otherwise unrecoverable for some reason.  In addition, keys are used for every transaction that you send, as well as for every address that you create in the "Receive Coins" section.

As such, it would be a good idea to keep track of approximately how many addresses you've created and how many transactions you've sent since your most recent backup.  Any time that sum of addresses + sent transactions is greater than 25, it would be wise to create a backup.  Then keep at least the 3 most recent backups somewhere safe.