When you're in the final burning dialog of the program, click on the "Encoder settings" button. This will bring up the MPEG encoder settings with the bit rate, which is ultimately the main deciding factor in how many minutes of video you will be able to fit onto a DVD. There's a list of presets, including "longplay" options. That's probably what you're looking for. I think there's nothing really special about a "longplay" DVD. It just has a low enough bit rate so you can fit way more than the typical 90 minutes on it. However, it does seem that when you're on the "longplay" setting, you got to lower the bit rate even further. So, if you don't mind some potential quality loss and you want to squeeze hours of video onto a standard video DVD, go for it.
You might also want to consider a dual-layer DVD, so you don't have to compress the material quite as much...or fit even more material onto one disc. ;-)