Hours old is a bit understandable. Day old is not. Check the date on tweets before you post. If it was a few days ago, we've already had it posted and seen it.

That said, if the post is decent, there's an argument to be made that it should be reiterated so that people who are late on the draw for whatever reason can still end up in the loop. It's not like there's finite space or that these posts are clogging the board. The 'upvote if you agree' posts do that, as does more subtle forum sliding. Ultimately, I don't actually think you need to worry about it.