I think long coats are very pretty and that is what I imagine a yorkie to have but I do know that a coat as long as a show dog would be insane for our pup. We are going to allow it to grow to about her knees (for now). Just as long as I can get it all even.
I look at a lot of different possible cuts and can't find one yet that suits her personality. LOL. We have a Min Schnauzer that we like to grow his hair out as well. They are so beautiful. But at times we do end up cutting his hair short for one reason or another (usually if he gets something stuck in his hair or the groomer trims shorter than usual.