Not trying to be a wise guy or anything, but a deer can move twice as far at 40 yards then it canat 20 yards before the arrow gets there. Even further if you take the deceleration of the arrow before it gets there.

Here is my reason/experience for doubting a shot with a compound at a whitetail even past around 25 yards. I was shooting 300fps setup at the time with carbons and I was shooting at a buck at about 35 yards. A shot that I took sucessfully more then once in the past and a shot I felt 100% confident in. The buck was grazing at 35 yards broadside alone and had no clue I was there. I drew back on the buck, and everything was right. I released my arrow. However at the point of no return on the releaseand the time the arrow got to the buch, he took a quartering away step.By the time the arrow got to him (believe me, it sure seemd like a long time), it didn't hit where I wanted it to. The arrow went exactly where I shot it though and itflew unobstructed. Nothing about the shot I felt was my fault. But the arrow still didn't go where it would have if the deer would not have taken that step/turn. To make a long story short, I caught the liver and one lung instead of the double lung and I had to let the deer expire overnight. I collected him in the morning. But it left me with a real bad feeling.

Below is a link to a little info on the amount of time it takes an arrow to reach a deer and how much a deer can move before it gets there. For those who may be interested (scroll down to my post):

http://www.huntingnet.com/forum/tm.aspx?m=240480&mpage=2&key=mph%2cdeer%2c move&#240618

Extremely well put IMO.