[dbolgheroni]

In general it's good to have products with reliability as a first class citizen, but the best way to keep data for lots of years is to replicate them onto a reliable media from time to time.

[harry_ord]

Apart from written down/printed well is there any other really reliable long term storage?

[bennettnate5]

Archival quality blu-ray (such as M-DISKs) can purportedly last hundreds of years and will outlast any electromagnetic events that would destroy other magnetic/electric-based storage mediums. As others in the thread mention, the key difficulty is reading and interpreting the etched pits on the disk hundreds of years after the spec is obsolete.