I've had long hair since I was 15 And I did grow it out to feel like a girl XD it worked too if only I'd tried to transition then I would have gotten away with it.

although awhile ago I can share some things.
what you've described sounds about right most pepole it grows at a rate of half an inch a month although it speeds up during pregnancy and slows down with age soo 23 inches (Which is actually even longer than mine at 18 inches ribcage length) and mine is pretty much at it's terminal length because I abuse it sometimes when I get bored with it XD
would take 46months for you assuming no trims or breakage more realistically 55 Assuming your hair can even go that long. If it dose then congrats you can be one of the girls I envy.

There are many things you can do to avoid it stopping growth at certain spots, First reason why it dosen't grow to a certain length is breakage, Which is my stopping hurdle, Hair drying it, Hair Dye, Brushing it when wet, heat treatments all damage it. My Hair sin as it were would be the dye.
What can I say? when I was younger it was a nice Raven black now it's just dreary brown. Anyway don't do those things towel dry which I know can be a pain if your in a rush and find a good conditioner that prevents breakage.
At longer lengths your more likely to encounter some problems washing it mostly in my case the hair ends up slightly more greasy at the roots and dry at the tips, So try to get a "mixed mood" hair shampoo if a similar thing happens to you avoid over-conditioning the roots.
If you have an unusual reaction to HRT or just aren't on it be aware you will have to wash it alot most likley T covers ->-bleeped-<- in grease it's so gross ¬_¬ but I know some girls just have greasy hair anyway without T. And that's fine but if you should avoid unnessercily washing it because washing away from of those useful oils that prevent oxidative stress from the environment and make it brittle and also be Aware HRT can totally change the personality of your hair... It did with me and there was an acclimatisation period of figuring out what it needed.
There's a final thing diet. I've never needed it but girls I know with longer hair than me swear by certain diets to get it there. These dies vary but usually they have in common is they are rich in Vitamin D, Fish oil, And foilic Acid.