The main limiting factor for us is the schedule for irrigation installation [which is driven, of course, by the schedule for planting]. As long as we are well ahead of the irrigation guys, we have room to tinker.
They don't usually start the irrigation system until there are nine holes shaped and ready [so they won't catch up to us and have to stop], therefore we have a bit more license to tinker around early in the project, when we are trying to get the style of the course sorted out. After that, there may just be a couple of holes where we're not sure what we want to do, and we will keep tinkering around ... we don't do it on every hole.
I have put things in the ground many times that I wasn't entirely comfortable with. On a couple of occasions, it was because I had to be away at some other project, and the contractor INSISTED that the hole be planted before I could get back because it was going to wreck their whole schedule ... funny how that never happens except when outside golf contractors are involved.
On others, I knew that we were building a green or feature that would be controversial, or borderline unworkable. Out of maybe a dozen of those, I've actually had to go back and rebuild part of a green three times ... one was absolutely not working, and the other two really was passable but the members just didn't like it. Still, I would consider those errors on my part, and I don't like making errors, so I get a bit more conservative as I go along. But not too conservative, as anyone who has played Old Macdonald would freely attest.
I should say that we are quite fortunate that we haven't done many jobs where the budget was so tight that there was no room to tinker. Frankly, since any new course is costing in the millions, I think it's crazy that anyone would be building a course where they couldn't spend a few thousand tinkering around to make it better. Nowadays it is seldom an issue for me because we are usually doing all of the shaping ourselves, and if there is any question about the cost of tinkering, I am happy to absorb the extra cost in order to get the hole as I want it.