It's awesome that you're having a good time with it!
I knew from the beginning (about 8 years ago) and was immediately supportive. In fact, I encouraged my SO to start going out to places other than her TG support group. We did have a rough patch for some years though, from about 6 months into our relationship onward. My SO was developing wings and flying and it seemed by far the preferred activity, and so I wasn't sure where it was all going. At one point I felt as if my SO would be a lot happier being free, without me.
But it all fell into place as my SO got used to doing everything in girl mode that he did in guy mode (except work) and for the last few years, things have stabilized tremendously. The CDing is just as much a normal event in our lives as going out to have pizza with friends. Well, it always was, but my SO prioritizes other things now too.