I am another charter member of the IBTC (itty bitty titty committee). After 15 months, I am barely an A cup. Every now and then, I get a "growth spurt", but the actual amount of growth is minimal. My breasts seem to get fuller, but not bigger.
Oh, well, they are bigger than those of our friend N, who is a cis woman and flat as a board. So I won't complain.