At our house a bully stick is a special treat. And I don't think it matters how many you have, when you have more than one they are going to want what the other one has, even if it is EXACTLY the same thing. Pet siblings are no different than skin siblings as far as that goes
I would never let my adult yorkie chew on a bully stick all day long much less a puppy. I think I've heard where they can harbor salmonella, and in my very unprofessional opinion, I would think that maybe a puppies digestive system isn't developed enough for that.
I would be a little scared to order them from someone I don't know anything about, i.e. e-bay. I would recommend that if you are going to continue to let them have them, make sure you get them from someone reputable.