Hiya Ben,
Do the source videos play without issue on your computer before you convert them?
I've converted entire 3 hour movies with no issue - there isn't a file size limit for conversion, there's just a limit in size to the SD Card you use (the one with the kit is 8GB). There's the character limit, but you also can't use special characters or symbols. You can try re-naming all the videos to something like "video1, video2, etc" to rule that out as a problem.
What format are the source videos? mp4?
Let me know!
Réna