If you are absolutely clear on everything you need to do in a golf swing and b) if you have already hit a lot of balls over the years...results should be nearly perfect WITHIN minutes. I can't fathom the thinking such as "it takes 90 days to make a slight grip change, etc.).
If the golf ball doesn't behave, something is wrong. Anyway, that's how I feel. Invariably the problem is a technical one because of a misunderstanding on my part, once that misunderstanding is removed, I fully expect the very next ball will be well struck.
An exception to this would be swing models that are convuluted/idiosyncratic (sp). They are doable, but take a bit longer.
However, if you haven't hit a LOT of balls, accurate knowledge is not sufficient as your body/nerves/mind is still learning how to make golf swings.