I have been asked this question a couple of times in person, and I recently saw the question asked of another blogger and thought that people might be interested to know how and when I came out to my wife.
I was always very shy at school, because I knew that I was different and was petrified that someone might find out. Consequently, I ended up being something of a loner and a misfit. I also had a crush on one of the most attractive of the popular girls in my year, which was fairly widely known. That shyness carried over into my time at university, where I still thought of myself as a misfit even though I suspect that others might not have seen me that way.
The result was that I never had a girlfriend all the way through school or uni. I had my first girlfriend in my mid 20s, and she was almost 10 years older than me. The term cougar would have been the perfect description for her, if it had been around at the time. She pursued me and I let it happen because I was flattered by the attention. It was a disaster of a relationship, and when I admitted to her that I was a crossdresser, she took it as a personal insult, claiming that it made her less of a woman. I tried very hard to make the relationship work, including the only significant purge (disposal of female clothing etc. in an attempt to stop crossdressing) that I've ever undertaken, and getting my hair cut short for the first time in about a decade. It didn't make any difference. In her mind, I was a transsexual and it was only a matter of time before I'd transition. The relationship ended, and I was far better off even though I didn't feel that way at the time.
After that disaster, I made the decision that I was going to be open with a potential partner very early in a relationship. If they couldn't accept it, we could both move on without having spent too much time in a relationship that wasn't going to work.
A few months later, I met the woman who was to become my wife. We met in a small outdoor food court area, and spent a couple of hours chatting. I walked her to her car, and as I watched her drive away, I found myself thinking "I could marry her." That was not something that I had ever thought of anybody before, and I was surprised to have thought it. We went out to a movie a couple of days later, then I didn't see or even hear from her for a month. I rang her mobile but it went to message bank. I left messages, she didn't respond. I'd all but given up when she got back in contact with me. Apparently her phone hadn't been working. We went out a few times and I decided that I had to tell her.
I was trembling with nervousness when I told her, but I knew that I had to do it before the relationship progressed too far. Her response was an incredible relief. I don't remember the exact words, but it was something like "Oh, is that all. I thought maybe you were bi." She later told me that she knew that there was something about me but wasn't sure what it was.
I'm pretty sure that somewhere in the discussion that followed, she told me that she could accept my crossdressing if I could accept her hobby, which I could. We've been together for over 11 years now. I'm not going to pretend that we haven't had disagreements, but my crossdressing has never been at the centre of any of them, or used against me. The reality is that we are both fundamentally lazy and our arguments tend to be about domestic chores not getting done.
My wife hasn't merely tolerated my crossdressing, either. Before we were married, we were trying to save up the deposit for a house, and during that time she talked me into spending $350 on a wig that I couldn't really afford, because she knew that the one I had didn't suit me and that I really wanted a better one. Not long after we were married, I wanted to have a professional makeup lesson and she went along and did it with me. When I wanted to get my ears pierced but was terrified of how people would react, she told me that if I wanted it done, I should just get it done, so I did and virtually nobody ever even said a word. When I wanted to go to Seahorse meetings in Sydney, she went with me to every one of them. Being interested in crafts such as beading and knitting, she has made me jewellery and clothes. We also share some clothes, particularly dresses that I buy at op shops, including this one, as I predicted back when I bought it.