I use "Bitcoin Core version v0.21.1". I have one wallet with several receiving addresses, I also encrypted my wallet with Passphrase and made a backup of wallet.dat and Passphrase.
I have just added a new receiving address. Do I need to make a backup again? Or I will be able to use my old backup and my new receiving address will continue to work if I will restore from a backup made before I got a new receiving address?
As I read on Reddit, Bitcoin Core wallet has pool of 100 addresses. Having less than 100 addresses does not need to make a new backup.
You need a new backup again, when a new key is generated.
Each key gives pool of 100 addresses, so my current backup will work for a year if I will generate less than 100 addresses.
https://www.reddit.com/r/Bitcoin/comments/1awx1o/do_you_have_to_back_up_your_wallet_every_time_you/