Some content is good at 15 minutes (I know its subjective), other videos at a hour aren't long enough (like the going deep ones).  So maybe if they go longer than 45 or an hour break them up. 

The shows that always have a lot of views (Like going deep) keep full length and Rocken (Thanks Charles) and the ones that just have a few views liven up by being short and to the point.  If people want more of those they will tell you:)