My personal perspective is that I get to tinker with my designs while they are in the dirt, so I don't feel the need to do more once they have been grassed, unless a client has identified a clear problem [like the safety problem on the 17th/18th holes at The National we fixed this year - but that was the first time in my career I've had to do that].
I have now done two courses that host a tournament on a regular basis, and there seems to be an expectation that we will tinker with those ad infinitum -- I worked on a change to the 17th hole at Memorial Park just this past month. Those changes are at the clients' request; I am not the driving force. In fact, such work is very inefficient for my own time management -- it takes me 30-40 days on site to design and build a new course, but then 2-3 days [including travel] to make some tiny adjustment to one hole that might change the winning score by a fraction of a shot. Generally, I'd rather not do something like that, unless a real problem has developed.
At Memorial Park, we are trying to get them to play the 17th as a drivable par-4 on the weekend, and the TOUR just wouldn't set it up that way on my original design when it was all carry onto the green. So we have moved the green back and the tee forward to the point that everyone will be able to get over the pond if they go for it. I would also note that the TOUR and the sponsor asked me to look at rebuilding the 9th and 15th greens to make the roll-off areas less severe, and instead of spending six figures to rebuild them, which was the default assumption, I suggested they bring in the collars about three feet so that more balls rolling off the green would stop at the top. This suggestion was motivated in part by my not wanting to spend several more days trying to rebuild them when the success really depends on the set-up.