Do I ever want another mammogram?

On one hand, they have found no safe exposure to radiation.  That means they have not found a  lower dose of radiation where there is no effects.

On the other hand, we are continuously exposed to radiation.  

This site describes amounts of background radiation.  Note that naturally occurring radon is about 200 millirems/yr, smoking is about 280 millirems/yr, whereas  is dental Xrays with about 10 millirems/Xray, and a chest Xray is about 8 millirems/Xray.  http://web.princeton.edu/sites/ehs/osradtraining/backgroundradiation/background.htm

 “The effective radiation dose from a mammogram is about 0.7 mSv, which is about the same as the average person receives from background radiation in three months. Federal mammography guidelines require that each unit be checked by a medical physicist every year to ensure that the unit operates correctly. See the Safety page for more information about radiation dose.”http://www.radiologyinfo.org/en/info.cfm?pg=mammo

Being exposed to large amounts of radiation early in life—such as atomic bomb explosions in Japan and therapeutic radiation for certain cancers— has been linked to an increased risk of breast cancer.

The risk for developing breast cancer later in life is related to the amount of radiation received and the age of the exposure. If someone received radiation treatment before the age of 20, his/her risk is very high. The same exposure after the age of 40 would give only a small increased risk.
X-rays and mammograms expose you to very small doses of radiation and have little, if any, impact on breast cancer risk. Any potential risks of screening tests like mammography are thought to be strongly outweighed by their benefits.

A mammogram is done with a special type of X-ray machine used for breasts. This machine produces low energy X-rays that do not penetrate tissue as easily as in a routine chest X-ray. This method lowers the dose of ionizing radiation to the breast while still producing a high-quality contrast image for doctors to evaluate. http://ww5.komen.org/KomenNewsArticle.aspx?id=7710

The modern mammography machine uses low radiation doses to produce breast x-rays that are high in image quality (usually about 0.1 to 0.2 rads per picture). Older mammography units delivered higher doses, and led to concerns about radiation risks. These older machines are no longer used.

Strict guidelines ensure that mammography equipment is safe and uses the lowest dose of radiation possible. Many people are concerned about the exposure to x-rays, but the level of radiation from mammography today does not significantly increase the breast cancer risk for a woman who gets regular mammograms.

To put dose into perspective, if a woman with breast cancer is treated with radiation, she will likely get a total of around 5,000 rads (a rad is a measure of radiation dose). If she has yearly mammograms beginning at age 40 and continues until she is 90, she will get a total of 20 to 40 rads. To put it another way, the dose of radiation that she gets during a screening mammogram is about the same amount of radiation from her natural surroundings (background radiation) she would average over about 3 months. http://www.cancer.org/docroot/CRI/content/CRI_2_6X_Mammography_and_Other_Breast_Imaging_Procedures_5.asp