It's my understanding that change addresses usually use the unused pool addresses, then every time you use 100 it will make another new 100 addresses to use. So you technically only need to backup whenever that mass generation happens.
I was told that every time you send coins and a change address is used, a new one is generated, so that there are always 100 addresses ready to be used. There is no mass generation. That also means that no matter when you make a backup, you have 100 sends left to make the next backup.
either way, I was under the impression that you only need one backup of your wallet and you're good.... as in for life, if your backup holds. But one could quickly go through a hundred transactions, and if one didn't periodically back up the wallet, one could lose the most recent transactions.
Anyway, maybe everyone knows this, but I didn't. My impression from reading stuff this past 2 months (I am green) was that one backup covered you
