At 4.5 years on E and still being on the Spiro post op, I can authoritatively say you are only beginning, only beginning. I fathered two girls who are 40 and 34 years old and was a single parent to them from ages 11 and 7 up, the oldest began her puberty and periods at 11, and the youger one began at age 9.5. Both of them were still growing into their 20's. If you get the picture that 10 to 12 years is a possibility for you, you are right.
The WPATH Standards Of Care V7 in a table at page 38 for MtF's lists things with a bottom time of 90 days to get going, and 3 years plus to get to full development, but the numbers on all the stats say "average" meaning YMMV -- your mileage may vary!! I recently had some new expansion of my bust line, so mine is still chugging ahead at over 4 years. Feels great though.
As said above, do not change your medication without your doctor's knowledge and advice or you will get terribly frustrated to the point of wanting to harm yourself. I have seen it. Trust your doctor too, and then settle back and breathe normally. Why the heck you took a vacation from the Spiro without the doctor's knowledge is more than I can fathom since it reduces the efforts of your Testosterone to make you boy so that the Estrogen can push you on to being girl faster. At most you have slowed things up an hour or two if that long, but without the doctor's say so, I think it was nutty.