Do the Dragons of Tolkien's works die a natural death, or are they like the elves and can only be killed in battle?
Thorin's speech at the beginning of The Hobbit suggests that it might be possible for dragons to die a natural death:
On the other hand, that could just mean that it's possible so far as Thorin knows. Tolkien never actually writes about a dragon who dies of old age. Certainly Smaug's boasting suggests that dragons get stronger as they age: