One solution to the problems you mentioned is to make multiple copies and store them in different safe places.
To solve the problem of getting wet and fading, you can laminate the papers, which is a guarantee of solving most of these problems.
To solve the problem of getting burned in a fire, you can store your papers in a fireproof box. I think if you take these steps, you can get rid of the problem of getting burned, getting wet or fading.
For extra security, you can store a copy of your wallet's private key in a bank's safety deposit box. This way, you can reduce the chances of theft or robbery.
Or we can simple prefer the method of fillippone - mentioned just a post above of yours. I really think laminating the paper and storing it for long term is a best practice because we can still lose it and it is still vulnerable to water and fire both, although storing multiple papers with different phrase's words printed on more than one pages is a good idea.
But we should not use them at all, paper wallet are old now but if we still want to use, then we definitely want to follow a easy and simple method of securing them, I would have encrypted it first so no one could use it, I would have a dedicated, water and fire proof safe from this, then I might not even use any other material than paper and won't even laminate it.