Just remembered that I have written the recovery seed phrase of my Electrum on a piece of paper somewhere in my place. I'm wondering what could go wrong since my place isn't too secured. How about trying to memorize it? Is it possible?
If you have two or three backups already in different locations, you can memorize it. But do not consider your memory as backup. So the seed phrase you memorize is not a backup.
That's why I said it has no drawbacks as long as you have a physical copy of that private key!
OP asked how secure is but only after mentioning he has a piece of paper with the seed from his wallet, I still don't see any disadvantages to it.
Although, the disadvantage I see in it is that I do not think someone can have just only one sees phrase. But if it is only one and not more than 12 words, I think if he has like two or three physical and offline backups, memorizing it is not a bad idea.