[autotravis]

Blockchain! But seriously, I'd do a rewritable optical media, a flash drive, and a spinning drive. I'd do checksums on existing data any time you write to it to ensure nothing has been lost. I'd also do some sort of versioning at each write and actually keep a full copy of the data before the write. That last part could get unwieldy if your data grows over a lot time.

And I would double each storage media and keep one set off site.

This is all a little much for anything less than a "I NEVER can lose this data" requirement.