Hi Gemini!
I don't know too much about Fibroadenoma tumors. When they appear it's common to have the tumors throughout the breast. They are generally not considered to be a pre-cancerous condition, but can interfere in the diagnosis of cancer b/c a woman with Fibroadenoma who feels a new lump may not go to the Dr to get it checked b/c she thinks it's just another fibroid.
It sounds to me like 6month check ups are the way to go for you. 6 months is long enough to notice change, but generally short enough to not cause harm if cancer does start to develop.
I'm not sure how the Fibroadenoma tumors will effect your breasts in the future -- I've never had one. It sounds like something that may come back.
Keep an eye on it, breathe deep, and go out for dinner...it's not cancerous!