In other words, one should have "redundancy" in mind. By spreading crypto keys worldwide, you can rest assured that your crypto funds will stand the test of time. A material like "Titanium" could be used for engraving your crypto seed that will last for a very long time. It's a very strong metal that's quite affordable. Something like the "ColdTi" cold storage wallet card made of Titanium, will suffice. Then, you'd place other copies of your seed on an image encrypted inside a .zip archive. That compressed zip file could be sent to various cloud storage services (Google Drive, Dropbox, OneDrive, etc.) for complete redundancy of your hard-earned crypto funds. In the event you lose access to the Titanium cold storage wallet card, you could simply resort to the cloud to retrieve your funds at any point in time.
There are hundreds of ways to safely store and protect your crypto against a natural disaster. All you need to have is a little imagination/creativity to prevent the loss of your funds in a blink of an eye. It's always important to let know your closest family members about how to get access (and make use of) your crypto in case you don't survive a natural disaster. As long as you have a "Plan B", your funds will never get lost. The Cryptosteel is definitely a good choice for storing your crypto for years to come. If you have the money to afford it, I'd say that this is the best thing out there that will help you protect your crypto against any natural disaster.
Nonetheless, it's good to know the various ways of securing your crypto for the foreseeable future. With good planning, you'll be able to rest assured that your money is secure no matter what happens in the real world. That's the beauty of being our own bank with crypto and Blockchain technology. Just my thoughts