Whether the dose is reduced post-op or not is up to the doctor.
Some continue prescribing the same dose, regardless if development is incomplete or not, as they believe that, in order to maintain a good quality of life, youthfulness, firm breasts and what they've achieved in terms of feminization, a high enough dose is required. Also, it may help protect against degenerative diseases such as Alzheimer's, and prevent obesity and diabetes. Several studies suggest estrogen may be cardioprotective.
Others suddenly perceive us as post-menopausal women whose only concern is to keep away hot flashes and osteoporosis so prescribe lower doses. The practice whereby estrogen is reduced post-op is also somewhat due to the fact that back in the day when non bio-identical estrogen used to be prescribed to transsexual women without anti-androgens, the thinking was that now that testosterone is mostly gone, one doesn't need such a high dose of estrogen and given the risks associated with such forms of estrogen, reducing the dose minimizes potential health problems. Times have changed though (we now take anti-androgens pre-op and safer forms of estrogen) so that this practice may be obsolete in the present day. At least, I think so but I'm not an expert in the matter.
Once again, my 2 cents. You have the right to bring this up when chatting with your doctor but in the end, they decide and have the final word. You can always find another doctor and get a second and third and fourth opinion. The ball is in your court!
I'm 11 yrs post-op and take a high dose of estrogen with some progesterone. I still believe that my genetic potential has not been achieved and so, with my doctors' approval, I continue testing different combinations all the while considering health risks and keeping them at a minimum. To each their own.