I don't think HRT has directly influenced my interests. I still like videogames, foreign languages, piano, books, animals, movies, writing... Pretty much everything I used to. I do think, though, that living more and more as a woman has changed the way I spend my time in a few regards. I'm far happier and more confident now, so I seek the company of others and socialise a lot more, I take a far greater interest in clothes, accessories and my general appearance because now I actually feel able to present myself in a way I like, and, on the more negative side of things, I've started to shun singing in front of others, as while I used to love it, I don't feel confident enough in my voice yet. :/
Oh, and I tend to notice boys a lot more now. ^^ While I always loved romantic novels and movies, I used to be revolted by the thought of myself being involved in anything of the sort, and took no notice of either boys or girls. Now, though... I can't say if it's something chemical or simply my starting to not hate my body quite as much, but I've found myself having silly little crushes on people for pretty much the first time in my life. It's actually fairly unwelcome, as I doubt I'd be able to even consider having a relationship with anyone for another five years or so, but it's definitely there.
Of course this is assuming that I, at four months, fall under the "extended period" you describe. :'D