Here is something I have always believed about the things elves made. Their armor, weapons, and structures would not be made by mortal methods. As a magical race, elves would use some kind of magic to forge their armor and weapons as well as build their castles and settlements. Because of this, I believe elven swords and armor would be immune to rust and the elements. Elf blades would never need to be resharpened. Their cities and artifacts may be covered in dust, spiderwebs, and expanding plants, but they themselves would be untouched. Even after thousands of years, their cities and artifacts would look like they were created yesterday. I am thinking of elaborating this in future fantasy books because the elves may be long gone, but their cities and artifacts remain.