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.