It's after you reconvert them to burn to dvd video ... that's the issue. Keep in mind that those files have already been squashed down in size from the original. I'm not mighty experienced at burning video in this scenario where it's already been downsized. Video more-so than audio is much more obvious to reconversion quality drops. Some people might be half tone deaf, but most people are not blind if they can see a TV.

Remember, these are video files not data files. So it's not a simple matter of combining the disks & burning. During the burning process, they get reconverted. Even if they're mpeg2, they still need to go through the muxing process. And I presume also reconverted I don't know. If you burn a 700 MB mpeg 2 file to dvd, does the end result on the dvd end up as 700 MB? I don't think so.

But then probably someone will come along & prove me wrong! lol (re: fitting several such video files onto dvd without problems - ie: trouble fitting them on or dramatic drop in quality or both.)

Most of my experience is with PAL video -> DVD (ie: over 200 MB/min for standard pal. Multiples larger than that for HD video!) Not something that's been dramatically compressed from a ready made dvd, & then reburned to dvd. For a start, all video dvd's are highly compressed video. A little like mp3. mpeg2 throws away information to help it reduce in size. 720 x 576 pixels for standard pal. For VCD then it's around 352 x 240 or 480 x 480 for svcd. So as you can see, the resolution of the video has been changed for a start. Not to mention colour loss, image definition loss, lower data rate, etc. Each time video is converted, information is thrown away.