Background: The CMS GLP-1 Bridge demonstration (July 2026-December 2027) expands access to GLP-1s for additional eligible Medicare Part D beneficiaries for a $50 monthly copay. Its long-run value depends on uptake, discontinuation, and which beneficiaries initiate therapy, in addition to policy decisions. Methods: We used the Future Elderly Model, a microsimulation of Americans aged 55 and older, to model the costs and benefits of expanded GLP-1 access to the newly Bridge-eligible population, assuming that it continues over a 10-year horizon and is accompanied by reduced GLP-1 pricing taking effect for already covered indications in Part D beginning in 2028. We compared a status quo with two expanded-access scenarios: high discontinuation paired with high reinitiation (Rodriguez et al.), and low discontinuation paired with low reinitiation (Understanding America Study). Each scenario was run for two different definitions of the Bridge-eligible population - a broad definition that includes beneficiaries with prior myocardial infarction or stroke and a narrow definition that excludes them. Results: Expanded access generated positive net social value in every scenario, from $44.3 billion to $58.5 billion over 10 years. Medicare net spending fell in every scenario, with cumulative savings of $21.2 - 27.1 billion, including $31.9 billion in diabetes drug price savings. Return on investment was 117 - 216% for Medicare and 198 - 346% for society. The eligible population mattered more than persistence. Net social value was 23 - 29% higher in the narrow population, because its initiators are healthier and have more to gain form access to GLP-1 treatment. Low discontinuation raised net social value by only 2 - 7% but raised Medicare drug spending, so ROI was higher under high discontinuation. Conclusions: Expanded Medicare access to GLP-1s is projected to produce substantial social value across a range of persistence and eligibility assumptions. Extending the lower demonstration price to previously covered indications would allow the program to pay for itself from Medicare's perspective. Because health gains accrue over many years, evaluating the demonstration only over its 18-month window would understate its benefits.