First encoding a video always take time counted in hours. Whatever the CPU you have. And 6 hours is not so big when people need sometimes twice this time.
Second reencoding a KVCD is REALLY something that you should not do.§ It does not worth the cost nor the effort. .The result is nothing but ugly.
Starting from that, you do not tell the spec of your sources. If there are MPEG1 with reso of 352*240(28
, then you don't have to convert them ! The DVD spec includes such format. All you need to do in such case is to convert the AUDIO to resample it to 48Khz if it is 44.1.
All you need is to change your tool to author (use DVDLabPro) if yours does not support MPEG1.
If your sources are other thing then you should try to put them on a DVDV either ! (still with an audio resampled to 48khz). Even if KVCD resolution are not in DVD spec, my pioneer can read them all, even on a DVD.
And finally if you can't use your source without reencoding them, then just forget the idea !