It's just my opinion, but it takes a whole lot out of the quality of your work when you do that. You'd be better off cutting something else out to make the time needed not having to speed up videos. When people, generally, take the time to post up a video or video excerpt, it generally tends to give people there's a pretty good reason you should watch this, or this is an important view point to observe. Observing not just what they are saying, but their overall body language used when saying it, it totally erased when you speed things up. Their tone, their body movements, their eye movements, it's all crucial to what's being said.