Flash memory data retention isn't that long unless it's periodically powered up, the higher the levels per cell the worse it is (so, SLC - single level cell, where each cell only encodes 1 bit with 2 values - has far longer memory retention than QLC - quad level cell, where each cell encodes 4 bits with 16 values).

Meanwhile as somebody else already pointed out, stamped CDs and DVDs will last decades (this is not so for recordable ones, though if I remember it correctly even those last longer without content corruption than QLC flash).