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Seed priming can restore age-induced loss of seed viability or longevity; however, these invigoration responses may vary with priming agents and seed aging duration. The present study investigated the effect of two potassium salts (K-salts) individually and in combination (1:1) on different lots of muskmelon genotype, MS-1 seeds stored for four consecutive years, from 2013 to 2016 under ambient conditions. The combination of K-salts significantly enhanced the percent germination of seeds stored for two years (from 2015 to 2016). Further, it also improved root morpho-traits of 10-day-old seedlings. The storage duration had significant effect on the seed surface bacterial and fungal populations. A significantly higher cfu mL^-1 microbial counts were recorded for 2013 harvested seeds on three different agar-based media compared to 2014 to 2016 stored seeds. Further, the Scanning EM and FT-IR study revealed the surface microbiological status and functional groups variations, respectively. Thus, aging-related seed coat microflora is responsible for deterioration of the seed coat. Osmo-conditioning cannot restore viability of seeds stored under ambient conditions for more than two years.