Why many say that 30 feet is high is because of shot angle on the animal itself, not the distance.

The higher you go the more critical the angle into the deer is. Remember to aim for the exit hole.

And as Greg mentioned, the higher you go, the smaller the animal looks and people tend to overestimate the distance and neglect to bend at the waist and shoot high.

If you have a laser range finder and range the animal at 30 yards, worst case scenerio, take one yard off, bury your pin, pick a hair and bring home the venison.