So heres the trick to this achievement if you don't feel like physically dancing for 10 hours. First off, the time spent navigating the menus does not count toward your 10 hours only the time spent dancing in a song. So what I did was started a new song, when the music started and the avatars on screen begin dancing hit your guide button. Now make sure you have a controller that is plugged in so it doesn't time out after 15 min. Now the song should freeze and so will your sillouette on the box. Now go to bed and when you think its been long enough, hit the guide button again but now finish the song. The achievement WILL NOT pop until you have let the song finished.