The normal version requires 78 Defence to wear, and lasts for 100,000 charges of combat before disintegrating - it cannot be repaired.
A corrupt version also exists, which requires only 40 Defence and lasts only for 15 minutes of wearing (degrades even while not in combat).
A good method of gaining something back from the item before it vanishes is to have your character die in the wilderness. You will lose the item but gain approximately 264,000 coins in return if you return to where you died. This method is more lucrative than alching the item before it vanishes. This can be achieved by poisoning then allowing your character to die, or getting a trusted friend to kill you.