Bitcoin Core these days generate HD wallet, so backup it once is good enough. Although doing it periodically is needed when you want to backup note of your address/transaction or avoid perform blockchain rescan which takes some time.
With descriptors available in recent Core versions you can create a Core wallet that is based on BIP39 or even Electrum mnemonic recovery words. You can even choose arbitrary derivation paths if you want. But frankly, it's not that easy and you need some trusted tools and a secured airgapped environment because you have to deal with extended private keys (xprv...) to accomplish it. You don't want to get those any near an online device.
HD wallets were an important improvement in Core, descriptors are a logical and welcome step forward for sure, especially with interoperability with other wallets in mind. Maybe, one day we get a simple to use mnemonic words setup for Core, too.