Video Size Limit
What is the video file size limit when using Adobe Presenter to import a video file onto a slide?
Re: Video Size Limit
As far as I am aware, there isn't one. However, you should keep a couple things in mind.
Session Timeout setting on Connect: The default setting for Connect to timeout an on-demand session that doesn't have any interaction from the viewer is 30 min. This means that if you put a 45 min video in Presenter, it will time out 2/3 of the way through the video (less if there is more to the presentation that doesn't require user interaction) and no longer track that individual's progress. So you may want to either have a shorter video that that, or up the timeout time in Connect (Administration > Account > Session Settings).
Keep it reasonable: Think of your audience, and what they are reasonably willing to sit through. a 3 hour video along with other Presenter content may be too long. In general, I try to keep to 15-25 minutes per Presentation, so my viewers can easily fit in one or two presentations when they have time, and it is easy for them to take a break between them, without risk of losing their place.