My case (well my road to HRT) is definitively different than other TS, but still with similar results. I started on hormones on a low dosage about 6 years ago. However my breast started developing immediately along with the itching and wonderful sensitivity. Growth was definitively at stages and during periods. However after about a year the growth pretty much stopped - and I was convinced that that was it. I loved the sensitivity and softness but their size left much to be desired.
For the last years I was pretty much "stuck" with very pointy and conical shaped pair that could definitively been noticed through pretty much any shirt (less so with thicker darker shirts, which was often the trick I used). Ironically, except for the very occasional joke about men breasts and age no one made a comment about them - Even when shirtless or in a pool or beach. Of course being so self conscious about them I avoided shirtless situations and if in the pool or beach, i would spend most of the time either under water (where I felt they are less noticeable, thus making me more comfortable), or putting a shirt or towel right after I got out and of course with back to the rest of the people as often as possible. It was definitively not he best of times - from a breast perspective, of course. At some point i pretty much stopped taking hormones all together (for unrelated reasons). The growth stopped altogether (thankfully the sensitivity never went back) and would only vary in proportions with my weight and based on weather. While all the women in my family are at least a VERY FULL C (including my sisters who was a D+ before reduction surgery, and my mother that has been a D her full life) I had lost all hope of any further growth or development.
Recently, now at 36 with little or no expectations whatsoever for further breast development I decided to restart my intake, but now at "normal" TS dosages. My hopes were that through some dieting and little fat redistribution I could make my shapeless A-Cup sized breast somewhat ore "normal". Was I wrong!!! My breasts went immediately in overdrive and the itching, wonderful sensitivity came right back. However, more noticeable than size was the their more rounder and fuller shape than they took right away. They are not so much bigger than before, but unmistakably feminine. They jumped right away to a FULL A or small but well defined B. Now if I wear a 36B Bra with a shirt, she shape is clearly outlined and is all mine. I love it. Never in my life I've been drawn towards bras, as I felt they didn't do much for me, so i felt more like a cross-dresser when wearing one (not that there's anything wrong with that, but I couldn't relate). Now it clearly makes a difference and I can see myself wearing bras a lot more often. Since I have to continue living as a male at least for a while (for work, family, and friend reasons) I would need to control myself not to overdo it LOL.
Since then, i have become a lot more optimistic, and of course I hope for a nice 36C which is my ideal size. But I must admit that I would be really happy with a FULL 36B as long as they continue to developed as shapely as they are. At 36 years old I really don't have much hope for it or any additional physical changes, but clearly growth has not stopped completely and it gives me something to look forward to. Particularly now that I'm back on HRT and this time for good. My next trip to the pool will be interesting. LOL. I think that I can still disguise it as gynescomatia, but I'll soon find out whether people stare or not.