I usually have less than an hour footage to burn on a DVD with DVDA.
This time I have 2 1/2 hours and I would like to know if I need to render it in Vegas in some kind of different way so that the quality is still good but still fits on the DVD.
You can fit 2-1/2 hours on a standard DVD at 3.8Mbs average bitrate assuming one 224kbs stereo audio track and not a lot of menu media.
Whether the quality is good enough is entirely up to your taste.
Note: DVDA will usually overestimate the prepared folder size and ask to render. The way around this is to ignore the messages, Prepare (not Burn) the files, then re-open the Project. DVDA will now report the correct (actual) folder size for burning.