I have 2 yorkies one is 5 lbs and one is 4lbs and haven't had any health problems...(cross my fingers) they are very energetic and happy. The parents were between 4-6 lbs and my dogs where the average. None of the pups grew up to be less than 3 lbs and I'm glad I got my dogs on the smaller end of the scale because of my health I don't think I could lift a 15lb yorkie. (Maybe a larger yorkie wouldn't hide everything under my bed! he, he) I do agree that really small yorkies under 3lbs could have a short life
be careful and good luck!