After lots of work, I made a video slideshow that came to about 4 hours long. I used Videowave without issue to compile all the video and output it as one giant .mpeg file. I thought all the hard work was over.

I've successfully used MyDVD before to create a DVD with menus and never had an issue. The only difference this time around is that I was planning on using a DVD+R DL to account for the length of the video and make the video as good quality as possible using the "Fit to Disc" option. I do have a Dual Layer Burner, unless the symbols on the front of the device are lying to me. I tried this multiple times using both a blank Sony DVD+R DL and a Memorex DVD+R DL when I thought that might be the problem.

So in MyDVD, I added a brief intro video, the main video, customized the main menu, and was all set to burn. I had no intention of adding chapters or making it much fancier than that. So I inserted the blank DVD+R DL into the drive. Windows recognized the disc and even Roxio recognized it and said I had 8.5GB of space available. I click Burn and the burning process appears to begin when the "Burn Disc" window pops up. The first step in the process is the "Encoding Video 1 of 2", which it breezes through in 30 seconds, since the intro video is short. The next step is "Encoding Video 2 of 2". This takes about an hour due to the length of the .mpeg file. But after it completes this encoding step, it stops and says everything is complete. It never attempts to encode the menus or burn the image. So what do I do now?

Thanks in advance for any help.

A standard 4.7GB DVD will only hold 60 minutes of video at best quality. Anymore and the video has to be compressed with the resulting loss of quality. For a Dl DVD the limit is a little less then 2 hours. I would never try to squeeze that 4 hours video on a DL DVD - the quality will be poor especially if you use "Fit to Disk". You could also first burn to an iso file or Video_TS folder and then burn that to the DVD using VIDEO cOPY & cONVERT. VCC does a much better job of compressing the video to fit on the DVD then Fit-to-Disc.
Also next time use some quality DVDs such as Verbatim and not the junk Memorex or Sony.

In addition to what Walt said, use the High Quality (HQ) setting, and burn to a Folder Set. I don't have EMC 8 on my computer now, but I believe the Folder Set was an option with that version.

Video Copy and Convert, a stripped down junk version of Disc Copier, did not start until EMC 10, so you will be using Disc Copier to copy the .iso file, or folder set, to a DVD.

Thanks Bruce on correcting my misinformation about VCC and DiscCopier