This article discusses the evaluation of the hermeticity of polymeric/epoxy enclosures for long-term implantation. The aim was to determine the expected lifespan of biomedical devices inside the human body under accelerated conditions using two medical grade epoxies, Loctite Hysol M-31CL and Master Bond EP40 Med, to prevent moisture ingress. The results showed that the type of adhesive used to seal biomedical devices is a critical factor in determining their expected lifespan inside the human body, and the EP40 Med epoxy provided superior performance against moisture ingress compared to the M-31CL epoxy. A mathematical model was used to determine the lifetime of the polymer-metal-epoxy encapsulation based on internal relative humidity, which closely resembled the experimental results. The study's limitations included visual interpretation to determine the day the internal relative humidity reached 55%, and the experimental tests were conducted under accelerated conditions. Further research is necessary to confirm the generalizability of these results to real-world conditions and explore other factors that may influence the lifespan of biomedical devices. However, the study provides valuable information for the design and development of biomedical devices and highlights the critical role that adhesives play in determining their expected lifespan inside the human body.