Once a woman reaches age 40 then it's time to get a mammogram done.
After turning age 40 you should have annual mammograms done and then continue the annual mammograms of the breast until age 55.
Then after you turn 55 you can switch to having a mammogram done every 2 years which is enough but if you want to continue getting an annual mammogram then you can do so as you wish just to be safe.
If breast cancer is detected and treated early you have a much higher chance of survival.