Thank you for your detailed response. It's funny, I once posted a comment here about maybe being OK with having sex with a F2M [no longer true, now that I know more about the phenomenon both psychologically and medically] and people jumped all over me about being "bi" not "gay". Whatever: practically speaking it doesn't mean anything either way because I'm legally and monogamously married to another man and thus sexually available to exactly one person in the world. If I should outlive my spouse and have an opportunity to date a woman, would I? Perhaps. But it would likely be a celibate relationship, more or less. While I still do have sex, I don't need it the way I did when I was younger, and I assume a decade from now it will recede even further into the background. That could open up other possibilities. All this is to say that identity categories are fuzzy and not even necessarily stable over the life course.