I can only remember one time that I changed my plan on purpose. I saw a guy do something that made much more sense than the way I had planned. Luckily, he was a few shooters in front of me so I had plenty of time to rework my plan and get it burned in my brain. I think I may have won that stage in my division. But, that is the only time I can remember changing it after the walk through.
When I am making my plan my goals are to play up my "strengths" as much as possible while trying as best as possible to minimize my long list of weaknesses. And, I try to not make the plan complicated. I have seen way too many shooters crash and burn after making a very complicated plan.