The recommended frequency of mammograms depends on a woman's age, risk level, and medical guidelines from different organizations. For women at average risk of breast cancer:

• Many major medical groups advise starting mammogram screening at age 40.
• Annual mammograms are recommended by the American College of Radiology and other experts until around age 54.
• Women 55 and older may switch to mammograms every two years (biennial screening).
• The U.S. Preventive Services Task Force suggests mammograms every two years starting at age 40 until age 74.
• Some organizations recommend personalized decisions about screening intervals (every 1 to 2 years) in conversation with a healthcare provider.
• Screening may continue as long as overall health is good and life expectancy is 10 years or more.
• Women at higher risk may need to start screening earlier and/or have more frequent mammograms.

In summary, women at average risk usually have mammograms annually or biennially beginning at age 40, with timing personalized by risk factors and doctor advice. Screening typically continues through age 74 or longer based on health status.