I do alot of this as I record my daughters dance studio shows and produce the DVDs for all the other parents. SHows are between 60 and 120 minutes. as others have said you need to render your project as a DVD Architect Video (and Audio) Stream (mpeg2 and AC3) files. The size of the file depend mainly on the bitrate you choose.
When you do a “Render As”, Select the “MainConcepts MPEG-2” File Type, then Select the “DVD Architect NTSC Video Stream” (or which ever template you need to use). Now you then can go into the “custom” settings and adjust the bitrate. 6,500,000 will get 1hr and 30min onto a 4.7GB DVD.
8,000,000 is pretty well ideal for a DVD, but you are down to around an 1hr 15min of video at that point. get down under 5,000,000 and the quality really sucks. around 1hr 45min I start thinking about a 2 dvd set. I have had very little ‘luck’ with DLDVDs (8.5gb).
Hope this long winded answer helps and is what u r looking for!
Peace,
J