Tolkein's dragons -ALL evil. never aging, so one can not hope that a dragon will finally die of old age and you can get its horde.
One poem Tolkein wrote was of a horde with a curse; all who kept it came to bad ends. The elves who gathered it, the dwarf who fashioned the nuggets into artifacts, the dragon who killed the dwarf, the prince who slew the dragon, the old king ... "He heard not the horns in the mountain pass, he saw not the blood on the trodden grass. But his halls were burned,his kingdom lost in a cold pit his bones were tossed."
And the horde ? "there is an old horde in a dark rock locked behind doors none can unlock, .... There sheep feed and the larks soar, and the wind blows from the sea shore. The old night the horde shall keep while earth waits and the elves sleep.."
Far over the misty mountains cold To dungeons deep and caverns old The pines were roaring on the height, The winds were moaning in the night, The fire was red, it flaming spread; The trees like torches blazed with light. The bells were ringing in the dale And men looked up with faces pale; The dragon's ire more fierce than fire Laid low their towers and houses frail.