When posting a link to a "Live" video, and that video won't air for hours and hours later, then that post will not likely be upvoted on SN, and by the time the video airs any upvotes it does get won't raise its rank much due to the "decay" in SN's ranking algorithm.

In other words, ... maybe hold off posting the link until maybe an hour or less before the time that the live video actually airs.

Otherwise, what happens is that another person might post the video again, and duplication of posts dilutes the value that SN brings.