"only" 7-8 hours?? If people only did 1/2 that, obesity wouldn't exist!! Anything over 10 hours is a little excessive, anyway, 15 hours is kinda freaky in my opinion. I think the whold idea with a game like this is to squeeze in that extra 15 minutes that you didn't think you could for some people, do to time constraints, or that 15 minutes that we didn't think we could. For me, I'm hoping it's getting in that 15 minutes of core training more frequently.