Unfortunately we treat lots of false positives, which leads to unnecessary chemotherapy and other treatments. These unnecessary treatments harm ones health so much that no study could show an increase in life expectancy by doing regular mammograms.
Screening mammograms do reduce breast cancer mortality:
https://pubmed.ncbi.nlm.nih.gov/33141657/
Annual mammographic screening at the age of 40-49 years resulted in a relative reduction in mortality, which was attenuated after 10 years. It is likely that digital mammography with two views at all screens, as practised now, could improve this further. There was no evidence of overdiagnosis in addition to that which already results from the National Programme carried out at later ages.