I've been looking all over online for information, but it's kind of hard to come by. I am an FtM but I would love info from MtF as well because, as I said, it's hard to find anything about it for the most part.
I read something along the lines of de-transition goes more quickly for those who have only recently transitioned, because their body spent so long in the last state versus the new one, and it's still the default biological process.
As someone who transitioned two years ago and is still getting more masculine as months go by, I do feel that I am not 'all the way there yet' and de-transition might take less time (God, maybe just a year instead of two years?). I don't have gonads anymore, but I was on hormonal birth control for 6 years before transitioning, so the ones I had weren't producing anything anyway so either way I've decided that I will get hormone replacement therapy as reversal.
My doctor said that I can come in for an appointment to discuss changing my hormones when I called (they don't do that over the phone, I am guessing). I don't think they will give me any problems because it is a gender identity clinic that sees a lot of patients and they didn't even require me to undergo a year of therapy or anything - just an 'assessment'. Plus I think they understand the injustice if they would say, 'sorry but you can't have estrogen and progesterone because you have a vagina'.