We had a previous yorkie with ears that stood no chance at all of standing (he actually had "spaniel type ears!" and was ever so cute looking - his ears were huge and if they'd stood up he would have not looked right!!
Our other yorkie at the time, Gizmo, had upright ears ... one ear up when we had him and then that went down, the other up etc until both stood up ..!
Our present girls.... Gypsy Rose had upright ears at the age of 8 wks and they never went down and that girl has loads of hair on them - we have never even considered trimming her hair! Gizzie's were upright too by the age of about 12 wks and againno hair trimming. What I am trying to say is that I personally believe that if nature intended them to have upright ears (or not>>!) that's often the way it is! Ana xx