Policymakers have been increasingly interested in psychological interventions for criminality that are both evidence-based and financially sustainable, yet the best method for estimating long-term economic benefits of reductions in crime remains unclear. The present study evaluated two modifications of a cost-benefit analysis model from the Washington State Institute for Public Policy (i.e., WSIPP model) that calculated long-term benefits using (1) an expansive method based on year-by-year arrest rates and (2) a summary method based on average arrest rates over the follow-up period. More specifically, we applied the expansive method to data from previously published studies that had estimated summary economic benefits for (a) a 25-year follow-up of multisystemic therapy (MST) and (b) a 9-year follow-up of MST for problem sexual behaviors (MST-PSB). Results indicated that (a) estimated benefits were more conservative (i.e., negatively biased) yet more stable (i.e., less variable) under the summary method versus the expansive method and (b) excluding years of follow-up with high amounts of missing data resulted in modest increases in stability under the expansive method, although negative bias of the summary method was also less pronounced in this analysis. Given the complementary strengths and limitations of the expansive and summary methods, we recommend an integrative approach that synthesizes results across both methods to yield more balanced conclusions. Implications of these findings for researchers, policymakers, and public service agencies are discussed.