When you do Share>Disc, you should have a dialog screen with two items at the bottom:
One is a checkbox for Fit Contents to Disc, and if that is unchecked, there should be a Quality slider. At least that's where it is in PrE 4.
If you keep your Timeline video to 90 minutes or less, the Quality slidebar should have no effect.
As long as the existing Timeline can fit on a 4.7gig DVD, then no compression should be applied, thus the slide should do nothing...
I had not thought of that. Now, in the case of the test file that I used for the screen-cap, the Duration was only about 15 mins., but I was also in PrE 4, so the Quality Slider, for short Duration Timelines might not be visible in PrE 7, or later.