There are really only a couple of reasons to be out and thus tell a partner early on:
1. A life in the closet is a life that is fundamentally a lie. I'm not talking about to other people - they helped create this mess. The hell with them. No, what matters is we lie to ourselves. We don't live authentic lives in the closet. We can't be ourselves, and that robs us of our lives! THEY don't get to live your life - they have no say in it. Why do you give them such power over you? They don't deserve or appreciate it.

2. Being out as trans is hard sometimes. I won't lie about that. Indeed, those of us who are out get murdered or commit suicide in truly alarming numbers. A lot of us will hold vigils over the next week for those trans who were slaughtered by a cruel and uncaring world. But - the more we hide, the easier it is for others to view us as subhuman and worthy targets of violence. The consequences of being out keep many of you in hiding. And yet, if you don't stand up and fight for your right to simply be whom you are, no one else will fight for you either.

Look - I don't have to be out. My voice is pretty good, I look fairly passable now, and I'll look better in the coming couple of years. I could go stealth, and return back to the closet. I choose to be out because I'd rather die while living life on my terms than exist in the horrible living death that characterized my life before. My life is fuller and richer now than ever before. Yeah, I lost stuff. A lot of stuff. Relationships, material possessions, friendships. Yeah, it hurt like hell, and I know I'm one of the lucky ones. Still, I've gained more than I ever lost - because what I have in my life now is REAL.