Even if you wait until the deer is in range/position you may still have to hold if it makes a sudden turn where they no longer present a clean shot.
They will certainly move, if you fiddly fart around long enough trying to aim.
Get that pin on the spot and get rid of the arrow. Getting on target and the shot off quick is something else that needs to be practiced, and few people do it. Three seconds or less. That's all it should take from the time you hit anchor to get the pin on target and release the arrow.