Their YT media plan is both good and bad. Good as in, they have a good schedule of releasing material, most of it timed well to their own themes and what's happening in the world. Bad as in, I hate it when they re-share a older video trying to pass it off as a "Recent Upload" in lieu of something actually new. They have been doing well with their Throwback Thursday posts though, some rare material in really good quality.
The newer celebrity/parody segments being released to Youtube do bring interest that keep the show relevant to those who haven't seen the show in years, decades even with kids of their own/ the viral video loving crowd. Seems that they do use their account for show promotion, but it's strange that they've had some upcoming season footage well before the big press announcement. That Wizard of Oz thing, for example.
They
really need to do more with classic sketches, though. I agree, rereleasing old clips and saying that they're new is annoying, especially when there are so many clips they have on Sesame Street's site that haven't been made available to YT yet. I certainly doubt they're going to go through the whole archive to find more clips, but using the clips they already have on the other site would only add to their views.