Izzy just turned one 12/29 and she is only 2.8 and I've never had her cut down....she has pretty long hair. You can tell by her pics in her avatar. Her coat is silky so I don't worry about the matting so that's why I let it grow. I wish I knew how to wrap with oil then her coat would be 10x better..lol.
With the groomer you have to be very specific on what they are allowed to trim...my groomer also shows and breeds Yorkies so he knows what to do. He only trims the ear area and butt area.