I've seen various tips on how to keep your nano s ledger safe, as well as the 24 word key phrase... Fire proof safe is an excellent idea! Also, consider storing the 24 word phrase in an encrypted file on a USB memory stick, then storing this in a different location (parents house for example). One other tip I came up with is to use a book to store your 24 key word phrase in, if you have a lot of books on your bookshelf this can be a nice place to hide it... (please note these are just my ideas and I'm not suggesting that this is what you must do, simply what I have thought about / read about over time).