There's archival Bluray format called M-Disc which claims to have a several hundred year storage life and to be "impervious to environmental conditions". You ca

There's archival Bluray format called M-Disc which claims to have a several hundred year storage life and to be "impervious to environmental conditions". You can get the writers fairly inexpensively, and the discs are $88 for 5x100GB on Amazon. I never believe the projected lives of the things-- but consider it like everything else to be part of a safety net. I burn the irreplaceable things to those in addition to a normal backup strategy.