Hrunting, the Sword of Beowulf

In Beowulf, hrunting was meant to be a sword that never failed. The problem was that in the fight against Grendel's mother the sword totally failed. The blade had been passed to Beowulf by Unferth who had failed to destroy Grendel with it, so it's thought his failure had been passed onto the sword itself.

To reflect this, the Hrunting sword gains power when dealing killing blows, but reduces in power if a day goes by without the blade slaying someone. I think this presents some interesting roleplaying opportunities. If it comes to evening and the wielder hasn't slain a for, do they just accept that Hrunting will be less effective or do they go on the hunt? Maybe they track down a petty street thief and gut them. Do they convince the rest of the party to venture into the woods to clear out some redcaps? Basically, does the blade drive the wielder to bloodlust? Surely this desire becomes worse on the second day when the sword is reduced to a mere d4 weapon.

Hrunting
Short sword (d8)
Special: If an enemy is dealt the killing blow with Hrunting, the sword gains +1 to damage for the remainder of the day. Hrunting can have up to +3 per day in bonuses in this way. However, if a day goes by without hrunting dealing the killing blow, it is reduced to a d6 weapon the next day, and a d4 if this happens the next day (it cannot go below a d4). As soon as a killing blow is dealt by hrunting, it returns to a d8 weapon.