The render time/speed is dependent on what's happening with the media. If you have a straight DV event with nothing or little happening to it, it will render very fast. If you have a blur, color correction, title overlay, composite, or anything that is shifting pixels around much, then it gets slow. Using event based FX, keeping preview at preview, using DV-only, these will all speed renders up a bit. As you use Vegas, you learn some rendering tricks that will help your workflow.