iPod Touch Video App problem with downloaded MP4 Youtube videos

Recently I've cooked up an awesome and very easy way to watch free movies on my half-month old iPod Touch. What I do is I download Youtube videos in MP4 format, load them up on iTunes, transfer the videos to my iPod (that's connected to iTunes) and after just a few moments the videos will already be found on iPod's video app.

The first time I tried this, with random Youtube vids that are mostly for cartoons, commercials, and other senseless crap, it worked like a charm. And the videos were in high quality MP4 format too. But the thing is, this doesn't seem to work on vids that are more than 5-7 minutes long, and that's a problem because my main target for exploiting this "hack" is to score free movies from Youtube. The way I actually do this is:

1. I search for a movie on Youtube (say, "David Gonzales The Movie")
2. Then I download ALL video clips (it will come in clips of 10 minutes each because 10 minutes is the time limit for videos uploaded by mortal Youtube members)
3. I load them on iTunes and transfer them to my iPod
4. Lastly, I turn on my iPod's Videos app to watch

I've tried this many times, but I can't seem to get past more than 5 minutes into each clip. I know something is wrong, and I'll keep trying to find out just what in the heck I should do to fix this thing. I'll update about this when I land on a solution.