They seem to vary a lot. My first Yorkie weighed no more than 7 pounds EVER ... Ozzie
weighed that at 6 or 7 months. (He's now 13.5) at age 9.
My first Yorkie's ears never did "leather up" and always flopped. They only stood up when he would be listening intently to something. Ozzie, however, has always had stand-at-attention ears, though they flop on occasion. If I put too much conditioner on him, I notice that sometimes his hair tends to do the wave!