This study was conducted to compare seed viability among 42 species after ten years of storage in the midterm storage complex ($4^{circ}C$, 30-40% RH) at the National Agrobiodiversity Center (NAC) Korean genebank maintained by the Rural Development Administration (RDA), Republic of Korea and to suggest the relative seed longevity and suitable monitoring intervals. The germination data from initial tests and after ten years of storage were compared to measure changes in viability during storage. The decline in seed viability varied greatly among seeds from -11.5% for Triticum sp. to 80% for melon. Coriander, crowndaisy, safflower, cosmos, Chinesebellflower, waxgourd, melon, castorbean, Welch-onion, hollyhock, wild barley, and tallfescue showed significant decreases in viability of 34.2%, 73.4%, 36.5%, 30.0%, 40.2%, 71.3%, 80.0%, 65.9%, 45.5%, 51.4%, 53.0%, and 33.5%, respectively. Gardenpea, soybean, perilla, onion, wild rice, Italian-ryegrass, and pepper showed a 15-30% decline in viability, while the viability of morningglory, adzukibean, maize, and Capsicum sp. decreased by 15% to 5%. Chicory, radish, Chinese-cabbage, bottlegourd, watermelon, cucumber, pumpkin, Cucurbita sp., groundnut, kidneybean, clubwheat, sesame, wheat, Triticum sp., rice, barley, orchardgrass, buckwheat, and wild tomato showed changes in viability of <5%. The changes in storage viability also varied within families. The wild types of rice and barley showed rapid viability loss and presented different aspects from cultivars. Since seed viability of species, classified as index 1 or 2, showed germination losses >15% after ten years of storage, a viability test should be conducted with five year intervals, while species with germination loss of <15% (in index 3 or 4) can be retested at ten year intervals.