I know people who have killed animals at much farther than 30 with a tradbow, I also know people who've missed them at less than 15 due to them reacting to the shot. I think the situation matters a lot. I will take a 30 yard shot an an animal, but everything will have to be absolutely perfect.
Personally, if the deer is looking your way, or on any kind of alert, I wouldn't shoot.
Here is a video from one of our very own that a great example of how fast a deer can move.
At the end of the day, we live with our decisions and letting an animal live another day because of lack of comfort is a shot is always a good decision, imo.