I wasn't thinking about starting until I was a year into my estradiol only treatment or when and if I reach later Tanner stages of breast development. At this rate, that will be much longer than a year. Both of my doctors were ambivalent about progesterone. Will prescribe it if I want, but aren't sold either way on effects yet. Not surprising, given there's not a huge n out there with a controlled study. My year+ timeline was just based on the fact that cisgirls typically have their progesterone kick in late in puberty.