Hysol 9313 epoxy adhesive, a crosslinked bisphenol-A type epoxy filled with glass flakes, will be used in the optic mounting joints of a space X-ray telescope. During the extended period of earth storage of the telescope prior to its launch, these epoxy joints will be loaded and must be dimensionally stable to maintain the optical assembly alignment. To evaluate the long-term shear creep behaviour of Hysol 9313 epoxy, its momentary creep curve and ageing shift rate at 21 degrees C, 27 degrees C below its glass transition temperature, were measured in its linear viscoelastic region. The ageing effective-time theory was then applied to calculate creep strains of this epoxy under tensile and shear stresses after it was aged for various times. Results were verified by comparing the calculated results with experimental data. Using the anticipated loading profile for these adhesive joints during earth storage of the telescope, the shear strain of these epoxy joints was calculated to be greater than the required 0.1% shear strain even 2 months after unloading. Alternative storage methods to minimize the creep stresses acting on these joints are therefore recommended.