How quickly does breast cancer normally metastasize?

Varies. Each cancer is unique. Some cancer cells have the ability to metastasize very early in their development while other can be slower to metastasize.
Variable. The peak incidence of metastases is within 10 years of the original diagnosis. However, breast cancer may be evident elsewhere in the body as early as at the time of the original diagnosis, or it can be found as late as 20+ years after the cancer is first diagnosed. Of course, many breast cancers are cured at the time of initial treatment and never metastasize.