If I am understanding what you are asking correctly... I think it's all about maintaining and your genetics.
For instance, when I started birth control the first time my boobs were faaaaabulous. They grew from a pretty flat A to a B. I was so so so happy. Then my insurance stopped covering that brand of birth control, and when I switched they shrunk again.
Now I am older and I have leveled out at around a 32 B. When I do massages and herbs I see super fast results, but if I stop (for instance, I was sick this weekend and didn't massage or take my herbs) they disappear. After a while the swelling you see turns into real growth, but you can lose it once you stop. Of course, this is different for many women. Some people can stop and never lose an inch, and others lose everything. I think you can sorta look into your family history and tell. For instance, my mom and I are the same build and when she was breast feeding she grew up to a D cup. When she stopped, they completely went away and she ended up getting implants to fix them. Because of that and how easily I fluctuate, I am sure I will be massaging and on some sort of maintenance herbs for the rest of my years lol
However, I had a friend that had a baby and went up to a D cup and they never went away. Like I said, I think there is no way to gauge it for everyone. Every individual is different. That is why it's important to get to know your body.