All of these points will definitely be taken into consideration for upcoming animation challenges. It sounds like a lot of people don't have enough time to finish creating their entries.
I do have some advice to get around this though.
Remember that this is an animation based challenge. That means that your entry will not be judged on whether it has shadows, or whether it has nice reflections, but instead will be judged on the quality and believability of the character's movement and actions. So here's my advice:
- Render your character by itself. Perhaps give it a surface to walk/run on, but keep it a basic plane.
- Feel free to give it shadows, but if they take too long, there really is no need.
- Reflections and fancy materials are not needed for the actual entry, make a simple render that shows the characters movement well instead.
Another tip that I feel would help people judge the entries:
Show multiple angles of the cycle so people can see the motion from all sides and really see what you did. There really isn't a need for much (if any) camera motion. Sometimes it can be best to have simple side, front, top and perspective renders to show.