And it just slipped my mind, easy to happen as it, hmmmm, day 5 or so off of HRT. Yesterday I tried to walk out through two consecutive doors clearly marked "In" at the grocery store, among other estrogen-deprived shenanigans.
I was on cyclic HRT b/c my periods at the time had stopped and I had only had one in six months, so much longer than you. The idea is that they want to keep your uterus in the habit of building a lining. But if your RE is content that building a lining is not an issue -- my BW from a few months earlier had shown my hormone levels to be not just at perimenopausal, but postmenopausal levels, sigh -- then he might not think it's necessary. I also had very bad experiences w/bc pills and the patch, but don't know if that would have been so in perimenopause. As long as I'm getting enough estradiol, HRT makes me feel fine, but not enough and it's worse than nothing.
I didn't have a mock cycle as my periods were regular and adequate on maintenance HRT. If you were doing one, all you'd need to do, as far as I know, would be to have your regularly "scheduled" period on HRT, and then start the larger doses of estrogens used for your mock cycle.
BTW, on your getting asked about adoption b/c DS is half African, did you see this on Slate? So . . . for all the crap we DE parents take for using donor gametes instead of adopting, there are people who don't approve of that, either!
Maggie (in VA)