IMHO I think 12 or 13 hours alone is too much. 4 or 5 hours is the longest I will leave Lexy, and not to often do I leave her that long. I don't think you can train one being gone that much either.
If you can afford to, you might want to get 2 Yorkies so they have each other to play with while you are at work. You might also consider getting adult Yorkies as well.
Either way, I still think 12 or 13 hours is a very long time for a Yorkie to be alone.
I hope this helps some!
