Enchantment of reposite I-III

Reposite would be an enchantment book that you can place on an axe (and not a shield) to give a strength effect for 2 seconds after blocking a hit with a shield. The enchantments primary aim is to give the axe combat advantages over the sword. With each level of the enchantment, the effect of strength with increase; reposite I would give strength I, reposite II would give strength II, and reposite III would give strength III. of course the cooldown for each level would need to increase to prevent this from being unbalanced, 10 seconds for reposite I, 15 seconds for reposite II, and 20 seconds for reposite III would make the enchantment exponentially better yet balanced throughout the levels of reposite.