The short answer is yes, -80°C will offer longer storage for all biological materials compared with -20°C. However, ideally you need storage temperatures lower than the glass transition temperature of water (about −137 °C). This “glassy” state has enormous viscosity and so halts all biochemical reactions. For practical purposes anything biological stored at this temperature will remain in “suspended animation” for the duration of storage.

Your question will also depend on what specific hormones your storing. Progesterone levels in serum stored at −20°C for up to 7 years have been reported but this may not be acceptable for the sex steroid hormones. A paper on this is Article Effect of long-term storage on hormone measurements in sampl...

FSH frozen for less than 11 months at -20 gives a mean percentage degradation less than 4% but by 2-3 years, mean percentage degradation = 23% Article Inter-laboratory validation of the measurement of follicle s...

Thank you very much for your inputs