Board Thread:Dark Souls II/@comment-208.88.255.214-20140325153841/@comment-4526779-20160229140045

It may be since your weapon's durability wears down as long as it is inside of an entity such as an enemy or breakable item (barrels, crates, etc.) and if you're staggering your enemies, they won't be able to get away as quick, and your weapon is inside of their hitbox for longer, resulting in durability wearing down quicker. This is just a theory though.