To avoid this situation, I could use PlayTube, the iPad app I recommended a few weeks ago, but that would mean I would have to use my precious iPad gigabytes to store the videos. I set out to find an alternative so that I could use my laptop computer because I have more gigabytes to spare on my computer than on my iPad. Anyway, I found my answer: a Firefox add-on that downloads YouTube videos as MP4s. All you do is click on the add-on link and follow the instructions to install the ialc extension. This add-on has such high ratings because it is so easy to use! It simply adds a download button under the YouTube video which you click on and select the file type you'd like.
Cheers,
Lesley