A good rule of thumb is that 60-70 minutes can fit on a DVD at the highest quality (about 8-9 Mbps).
On a dual-layer DVD, you can fit about twice that much.
So you should be at very good quality.
Steve has given you some rough guidelines on Durations that will fit onto a DVD-Video.
However, there might be some confusion about what you're asking and how it's asked. First, all DVD-Videos are compressed with the MPEG-2 CODEC. Pretty much the same for BD also, just with different CODEC's. There is no way to create, author and burn a DVD-Video without compression. It is part of the DVD-spec.
What I believe you were asking is not about "compression," but bit-rate, the Transcoding settings. These are often accessed via a "Quality" slider, in some software, or maybe through dialog boxes in others. Though the DVD-spec allows for a combined bit-rate of slightly over 9MB/s, it's the video's bit-rate that you would be concerned with. To account for spikes and also the combination of Audio and Video, a bit-rate of about 8MB/s is the realistic max. Many suggest that for playability on set-top players, one not exceed 7MB/s. If we take that as our maximum Quality, you would end up with the Durations on Steve's lower end. If one can accept slightly lower Quality, then the Duration gets longer. Much will depend directly on the type of footage contained on the DVD-Video. With a lot of fast motion from either the subject, or the camera, one will begin to see a visual loss in Quality much sooner, than with static shots containing little motion. This is taken into account by multi-pass Transcoding schemes. PE does this with a 2-pass Transcoding scheme. Hollywood uses Transcoders that might be 30-pass, thus factoring in all aspects of the footage and setting different bit-rates for each section, or even by frame. The people running these Transcoders are also highly trained and highly paid experts, who do nothing else but Transcode.
Many folk have gotten over 2 hours of footage onto a DVD-Video. Yes, the Quality goes down, but might still be adequate, depending on the footage. Only one's eye can tell them if the Quality is acceptable.
>space required was 3.35 GB. Is this with or without compression?
By definition, a DVD is highly compressed when edit video is turned into viewing video
For SD (Standard Definition, what goes on a DVD) it takes about 13Gig per hour of edit video
That is compressed into MPEG-2 and then converted to VOB to go on a DVD
Exactly how much you fit on a DVD, at what level of viewing quality, is a subject much discussed
Hollywood studios use multi-pass software and will also set coding options by scene, to get the best possible quality
If you have a lot of motion (filming a soccer match) you can fit less high quality video on a DVD
If you are filming a lecture with someone static on stage, you can fit more and still retain quality
Thank you all for your advice.
I will keep each DVD to about 60-65 minutes to insure decent quality.