don't worry about this. i do the same thing. i work 8 hour days, but it equals out to Kash being alone for 10 hours because i leave half an hour early to drive to work, and it takes me half an hour to get home (that's 9 hours), plus i have my lunch break, but i can't come home to see him because i work too far and gas is costly (so that's 10 hours).
i keep Kash in an x-pen with a pee pad, water/food, toys, and his crate. he does fine with it... he's just overly excited to see me when i get home. if you read other threads about this same situation, most people agree that yorkies don't REALLY know how long you've been gone, whether it's 10 hours or 10 minutes. i get the same reaction from Kash when i leave to take out the trash as when i come home from work. the same bouncing, happy-to-see-me puppy.
i've been doing this with Kash pretty much since i got him about 3 1/2 months ago. and no problems thus far.
here's the thread i mentioned about a similar topic:
http://www.yorkietalk.com/forums/gen...yorkies-3.html
good luck!