I stayed on the same dosage post-op, but I also started off (while pre-op) taking something well within the cis menopausal woman's range. (And still got great results, including T levels squarely in the female range.)
Honestly, my endo always says it comes down to the patient's feelings and results, assuming they're otherwise healthy; she doesn't even believe in estrogen blood level testing, since that doesn't reflect how much E is being used by the body's receptors and can be wildly variable. Basically, if you don't think it's working for you, ask for a change, but the dose amounts themselves don't mean much. It's educated guesswork to figure out how much was needed to suppress T versus contributing to feminization, and everyone is different.