Why does it take a long time to get the effect of general anesthesia?

Hi doctor,

I have been told many times following surgery that it took a long time for me to get the effect of anesthesia. I even remember some anesthesiologists getting upset with me as it was taking so long and the attending nurses defending me. Last time during my surgery, I spoke with the anesthesiologist before the procedure about this issue. He assured me that he had many ways to make certain that I would get the effect easily and he could monitor it well. After the surgery, he made a point to come to me and said that I was correct. I took a long time to get the effect of anesthesia. I have been told in the past to breathe differently or more deeply when the mask is on, but this does not make a difference. A few years ago, when I was having a procedure, the anesthesiologist asked me if I wanted light anesthesia. I had never been asked this before. I asked her suggestion and she said she would go with the light anesthesia. Unfortunately, I woke up during the procedure and it was very unpleasant. So, what are all the possible reasons for a person taking a long time to go under anesthesia? When I was younger, this was not an issue. This began when I was approximately in my mid 40s. I am a postmenopausal woman. I am not taking any supplements or medications other than a multivitamin.