This may be a no-brainer for some of you but this is what I found out this weekend, thanks to my husband....he's always right!!
Usually Samson has all of his toys laying on the floor all day long and it seemed that he just wanted to play constantly which really wore me out. He would just sit there and bark and bark until you threw his toy. My husband cleaned up the living room when we got our carpets cleaned and when they were done we only had one toy on the floor for Samson. He wanted to play for a little bit but after that he got his bone and layed on the couch nice and calm. So......I believe (for some yorkies) that if you always have lots of toys laying around they are going to want to play constantly instead of just playing for a while and then taking a break. It's like they get too stimulated with all the toys and aren't able to slow down or take a break.