What do you mean by learn your key by heart? Memorizing the seed(s)? That's not a good choice. Even if you can remember the mnemonics with some tricks, nothing guarantee that you can remember it tomorrow. Printing the copy is better as you mentioned, as long as you store it securely. Buying a wall safe is probably a good idea but I won't put it open where people can see it as if you tell people "hey, there is something valuable here".
Seed phrases are meant to be memorized especially in emergency situations. For example, if a person is trying to escape from authoritarian regime or bitcoin-unfriendly country or simply wants to transfer wealth to another country he has to memorize his seed phrase and write it down again when he successfully crossed the border. Hardware wallets, paper wallets, seed plates are all good for safe storing and holding, but it is almost impossible to transfer those across borders. All your physical backups will suddenly become irrelevant and unsafe, because you obviously can't leave them behind and can't risk transfer them since they can and will likely be confiscated by evil government.