Pete,
Tom has it right, naturally. Over time, I also require less and less wiggle room. Usually, moving a hole to save one tree means you take out another one of equal value. And the whole "save it" becomes less desireable. How many times does an experienced gca have to save a nice tree, right in the line of play, before knowing that eventually, it has to come out?
That said, I do flag my tree corridors myself. One of the surpises of my career was learning that a well known gca told the contractor to go 100' either side of the centerline and clear, rather than putting any sort of artistic look on it. I usually use long, graceful curving clearing lines, believing they look more natural and/or artistic. From time to time, I find that I redo the entire thing, zigging when the plan shows zagging, etc. as the curvalinear tree lines just happen to fit better in some other configuration and DO save more signifigant trees.
I have come to realize that the inside points sort of determine how wide the corridor looks. I also note that oaks need wider clearing than tall, skinny pines, etc. Also, if I know there is going to be some kind of cut or fill for whatever design reason, it rarely works out that I can change that to save a tree.
So, I agree with Tom, that over time, as you learn what works, you are more inclined to clear out to the limits, maybe saving trees within the last ten feet of the proposed clearing line, but the whole idea of sequential clearing to 25 feet, then 50 feet, then the 100-125 feet is kind of a waste of everyone's time.