Generally speaking, cisfemale breast growth is completely up to genetics and usually takes about 10 years from "start" to "finish". Growth spurts can happen though, just like with height, but genetics will play the largest role in your final size. You can however do things like breast massage to promote growth, and in the developmental stages will likely promote a permanent boost, but no guarantees of course. As in ciswomen though, growth rates in transwomen vary wildly. It's kinda like playing poker, you get what you get, and while there is some strategy, it is still a game of chance.
I am early into Stage III myself probably, been there for about a month now (after almost 11 months of HRT), and I expect to be there for several more months. I expect it to take me 2-3 years to reach an ideal point where I can then reasonably decide to have BA or not. I'm still not on a transition dose yet though, so who knows. My E and T levels are both roughly half of "normal" for their respective genders, but if things go like I'm hoping they will then my dosage will be bumped up in about a month and start tilting the scale more towards the E side...
P.s. My butt has always been pretty nice, but I do like it more in recent weeks. <3
