- Seed phrases should never be memorized, nor written on a mobile device or computer. They can be written on paper or in a book that shouldn't be visible to external members and should be strongly protected.
Remember, ink can fade over time
https://bbs.boingboing.net/t/which-inks-fade-fastest/96814And this is why you make multiple copies and store them somewhere safe, create new ones after a certain amount of time and repeat the process until you die or probably be unable to do it. It's a pretty straightforward approach to keep your funds safe, and even if inks fade, it will take a long ass time for it to do so, and you will always have time to replace those writings and create new copies of your seed/passphrase.
That is true, you can always find a way how to create copies of your seed phrases and secure it. In this forum, there are even threads how to safely and securely store your keys, your options on how to implement it.