I don't want to make things difficult for myself, I save my seeds in 1 flash disk and 1 special book because I'm the type of person who is forgetful so I think a flash disk in a book is the right place to store my seeds.
I don't trust flash drives, hard drives, or any external storage device of that nature because they can get damaged and the files inside will corrupt, including your seed phrase and other valuable documents you saved in there, but saving in a flash will be a bit better than leaving it online in an email or so because anything connected to the internet is very risky and can easily get hacked.
Writing your seed phrase down in a special book is more secure and preferable than using an external flash drive because it will be there and will not corrupt, but if someone has access to it, your coin is gone, because unlike flash drives, you cannot put a password in a book unless you use some encrypted words that only you can interpret, and you can also duplicate the papers because of natural disasters like fire outbreaks, water, and so on.
If you write the seed phrase in a special book and are afraid other people can access it, you can use tricks like changing 1 or 2 positions of the words. That way, even if someone steals your phrase, they can't access your wallet. (You just need to change the position of the two words, no need to change too much to confuse yourself).
Also, I think we should have a better storage device than paper because paper is very perishable, as you said. Small sized steel plates as mentioned by Crypt0Gore are a better solution than paper.
Maybe if you have a risk that the seed phrase written on a special book might be stolen, then you should lead ill-wishers down the wrong path? Create a fake phrase and leave it where thieves can easily see or find it.
I would not store the real seed phrase where it could be easily found by people, outsiders and strangers alike. I mean, there is no need to keep seed phrase on the coffee table or under the computer mouse pad.
Regarding changing the position of some words in a phrase, the main thing is not to forget where and how the phrases will be replaced. Therefore, it is better to leave some
keys for yourself so that you can decipher this trick. Memory is not a permanent thing and can distort data. It's foolish to rely on that only when your savings are at stake.
The choice of paper or metal as a method of storing phrases has already been discussed many times. Anyone can carve a seed phrase even on wood or plastic, this is an individual choice and risks.