The answer to your question is a strong ymmv. Each of us is different. For me, a year ago I needed forms to fill a 36A bra, now, after 12 months on hrt I am half way between a 36B and 36C and still growing. These on my 5' 10" 170 lb frame have me very happy. Some gals on this site speak of much greater growth and some say that they are still a AA cup after years of hrt.
I have to add that while my physical changes are very enjoyable, the mental and emotional impacts are what has changed my world. I could probably very reluctantly give up the physical feminization but I would never want to give up the feelings that have come from hormone therapy.
Anne