Using a constant bitrate of 2,848,000 - I managed to get almost 4.5 hours on a DVD. Now the quality isn't great, but at least I am starting to get somewhere. Now if I can just streamline the process for when the FINAL build comes, I should be ok - but I have yet to test out an actual PREPARE or BURN.

Half-D1 format
 

If you are going to cram a lot on a DVD, you can try half-D1 format. I've done this many times under PAL (352x576). With NTSC it will be 352x480. Looks funny if played on a PC, but DVD players play it back correctly.

You don't want to use CBR for the ultra long stuff. 2-pass VBR is best. If the Main Concept MPEG-2 codec can't handle it, try a freebie like HCenc.

What is this like Half D1 like as far as quality and stretching of the image to fit on a TV? What bit rate should I use in this case? I am using Marks Bit rate calculator and I don't see a setting for half D1. Is that in Vegas?
Thanks for heads up, if I can get the info from you, I will give it a try tonight!

Does anyone know how I can get half D1 format? Do I just change the size in the "Video" tab under NTSC video stream DVD? Will this still render out to full size? Thanks

Also, can this be done if the project is finished and waiting to render?

David, forget about trying to do this with Vegas & DVDA as, for a 6 hr. DVD, the bitrate will end up being so low that your picture quality will be absolute garbage.
Do it on 2 discs and accept the poor quality that I know you're going to end up with.

Here's a comment about bitrates from John Meyer on a very recent thread on the Sony Vegas forum.

The important thing to understand is that the ONLY thing which determines file size -- and therefore how many minutes will fit on a disc -- is the bitrate. Resolution doesn't matter. If you encode 320x240 or 1920x1080 at 25 mbs, they will both end up at exactly the same file size. However, lower resolution requires fewer bits per second in order to achieve the same temporal quality (e.g., "mosquito" noise around fast-moving objects).