Understood. I had some reservations like this initially. However, mentally and emotionally, I could not look at one healthy breast with the thought of "what if it comes in the other breast then I am back under the knife again". I think it would have been very overwhelming. In doing the double mastectomy, that too assisted with that.
You are correct, you can be monitored and it is your decision. You must do what is best for you. In my journey, I find that this impacts each person differently. A lot of support groups, when they get to discussing chemo/radiation and medication...I cannot relate and look to find those most closely relating to my own journey. It's tough but you will get through this!

I had a lumpectomy in my left breast in 2005. In 2024, I had a recurrance of cancer in that same breast, and a masectomy was recommended because I did not want to go through chemo and radiation again. I chose to have a double masectomy so I don't have to worry about breast cancer going to the healthy breast at some future date. I do not have to have chemo or radiation. Many women I know who have had a masectomy- just one breast - have struggled for many years with a prostetic for just one breast, or have opted to have reconstructive surgery, which is not a quick fix and involves more surgeries, etc., and the results are not always that great which could involve more surgeries, especially if you have unrealistic expectations. It's a very personal choice. My main consideration was avoiding, at all costs, going through chemo and radiation again. After my experience in 2005, I will say that the "healing" process from chemo takes years... I didn't feel "right" until at least 6 years had passed, and some physical changes that happened during chemo became permanent and never improved, I just had to learn to live with them. Good luck on your journey, it is my belief that what age you are right now will help make your decisions of what path you want to follow for your futur years.