I think some people forget, and some don't. In my case, my family sees me as Bev, except for my son, who doesn't see me often. At work, it's a different story. A lot of it has to do with acceptance. Almost everyone uses gender-appropriate pronouns, except for one or two, who "forget" to use them, and usually it's in front of a customer. I'm settled in society enough now that I look at the customer, give a questioning look, and the customer looks back at me, like "is that person crazy?"
Long ago (seems like it), one co-worker called me 'he' in front of a customer on purpose. When that coworker left, the customer asked me what his problem was, and I told her I was lesbian. I said "I think he thinks that lesbians must really want to be men, so he calls me he".
Wow! What a reaction. She went after him and lit him up like a Christmas tree! He hasn't done it since.....
But, back to your question.....no. Most don't forget. It's just that new people don't know, or they didn't know me long ago, so there is nothing to compare to. They accept me as female, and call me she, her, etc.
But those who knew you, well......that's why so many of us used to go stealth. Now, with internet info, it's pretty tough to maintain it.
Bev