I agree, and there needs to be a mechanism to automatically save and ship add-on items when the conditions are met for free shipping. And to your point about a

I agree, and there needs to be a mechanism to automatically save and ship add-on items when the conditions are met for free shipping. And to your point about attaching them to a prime order, I would have to imagine Amazon is aware of this limitation and I wouldn't be surprised if they add this feature soon.