It's not a limited number of uses; it's a limited number of free uses. Subsequent uses merely require stress expenditure.
Thats not true. Subsequent uses are simply evocation of the same nature. The enchanted item has a set number of uses and after that it is drained. Such as Harry's ring. In Dead Beat he was too tired to use spells and he had run out of uses on his ring and hadnt been able to recharge it. They refference that an enchanted item is a "spell in a box" once its out its out.
Not every word JB rights is a conspiracy. Sometimes, he's just telling a story.
Sure. Would that be a better way to go?