For over two decades, federal policies and case practices in child welfare have shifted to prioritize legal permanence for children in foster care, and increasing numbers of children have been placed in permanent adoptive or guardianship homes. Despite this change, little research has examined the long-term stability of legally permanent adoptive and guardianship homes for former foster youth. This study used child welfare administrative records to track a population of 51,576 children in Illinois who exited foster care through adoption or guardianship for ten years or until the age of majority. Univariate and bivariate analyses were conducted to describe the population, and a multivariable Cox proportional hazards model was estimated to examine the relationship between child age and discontinuity, controlling for several pre-placement characteristics. Results indicated that the vast majority (87%) of children did not experience post-permanency discontinuity. In addition, African American children and children who had more moves in foster care had a higher hazard of discontinuity, while children placed with siblings and children who spent three or more years in foster care had a lower hazard of discontinuity. Study findings also indicated that prevention efforts should be targeted at families with adolescents. This study contributes significantly to the scant literature on long-term outcomes for adoptive and guardianship families, and suggests several areas for future research