For me, I see very little point in doing it. First, I would have no idea of the history of the other body (medical or otherwise), and second, what advantage would it really provide me with? I already live my life as a female, I have a nice hourglass figure, have plenty of people who express attraction, I have no nerve damage from any surgeries, I have nice breasts, I already have children that love me and I'm already more well-known as a female than I ever was as a male. If anything, it would be an unnecessary risk for myself and it would also take the opportunity away from somebody that may benefit from it much more than I would. So, my answer is definitely "never".