: No, no you silly demi-not-quite-almost-god!
: The knowledge still exists, in potentia. If anyone knew how to make rings, the ability for them to be made is still there
: So therefore the rings shouldn't fade. Nothing intrinsically "magical" about the rings have dissappeared, so why on earth (middle-earth) should they fade?
: Certainly, no elf, nor any other smith has the knowledge, but the potentia is still there....

: Gandalf

I can think of nothing better to be the (demi?) god of than wine and revelry. :)

However, in response to your argument, ME is replete with examples of singular achievements that cannot be repeated. Start with the Two Trees, then the Silmarils, the Palantiri (possibly) and the Rings. Arda was irreversibly marred following the ruin of the Lamps. The list goes on and on.