Hey dude... I'm still trying to figure it out myself. It definitely seems to be the same people most days getting the upvotes. I haven't quite figured it out it's determined by how many Dtube videos you've posted previously, or how high your reputation is. Some people get the vote literally every day, I've noticed some have gotten it twice in one day, so I think quantity might be the answer here.

There's also a factor of the timing of your video. Once you start to get the vote semi-regularly, figure out which times seem to work best.