FYI: I'm IS.
I'm 35, and I've noticed it's changed, but not my normal everyday voice. I used to do goofy voices, and I've found I can't do voices I used to.
Now I don't have an pretruding Adam's apple. But I find weird that, at work in a shirt and pants, people think I'm a guy. In my street clothes, people think I'm female. I was recently told by a complete stranger that I look and sound androgynous. Which could explain why I can't gender my own voice.
I've tried two apps that tells you pitch, but since I've always fluctuate my voice when I speek, I can't get a clear understanding of my voice.