The elite sirenic chaps lasts for 100,000 charges of combat before degrading to nothing. Once equipped, it instantly becomes untradeable, even if it has not been used in combat. Elite sirenic armour can be repaired by using a new piece of the armour on it. When used inside elite dungeons no charges are used.
Losing the elite sirenic chaps by being killed in the Wilderness will result in a single ancient scale being dropped regardless of item charge.