It lasts for 10 hours of combat before degrading, and then may be repaired by Bob in Lumbridge or at a Player-owned-house armour stand. It should be noted that the bow does not degrade in increments, and its stats stay the same for the entire 10 hours. The bow will not degrade if it is simply worn. It must be used in combat in order for it to degrade. The bow costs 2 million coins to repair at Bob's Brilliant Axes, or 1 million coins at an Armour stand with level 99 Smithing.