Purpose: To determine the frequency of insert changes for combined maxillary and mandibular implant overdentures (IODs) using the Locator Legacy system and to assess the survival of dental implants with IODs. Materials and Methods: This retrospective audit reviewed clinical records with up to 12 years of follow-up from 785 patients who received IODs using the Locator system at a dental hospital. In total, 151 had a combined maxillary IOD opposed by a mandibular IOD and of those, 37 had data retrieved using a minimum data set. The frequency of insert change was recorded and descriptive analysis was provided by means and SDs for continuous variables. Frequencies of categorical values were reported as percentages. Results: In total, 222 implants were placed in 21 men and 16 women with a mean age of 67.5 years (SD 8.8). All patients were reviewed at least once. Maxillary and mandibular IODs experienced 1.9 (SD 2.0) and 1.2 (SD 1.2) mean insert changes per patient, respectively. The mean time (SD) between initial and first insert change for maxillary and mandibular IODs was 3.4 months (SD 3.2) and 6.4 months (SD 7.2) and between the first and second insert change was 9.9 months (SD 9.0) and 10.0 months (SD 8.3), respectively. Implant failure was 21.6% and 2.7% in the maxilla and mandible, respectively. Conclusions: Clinicians should anticipate the first insert change around 3 months for maxillary IODs and 6 months for mandibular IODs. Subsequently, the second insert change should be expected around 10 months for both maxillary and mandibular IODs.