Hard drives from the last 20 years are now slowly dying.
Tape suffers from bit rot too. Radiation doesn’t target just HDDs and SSDs. Look, I don’t know what to tell you. I deal with a lot of large companies and I lived through tape’s hayday. The cost to archive data on disk is not high and companies don’t have issues doing it. Having it on disk prevents bit rot, because the pools are massive and are auto-healing. Also, the only way that your archive is not going to be long term is if humaity ends. Seriously, what do you think it would take to destroy a multi-AZ glacier archive?
Ultrium media has a lifetime of 30 years after the first write to the cartridge, and that’s assuming you write to it up to the maximum number of full writes (260).
Assuming you write to your cartridges once, store them (and the drive) in an airtight dustproof box, and don’t expose them to extreme temperature or humidity, you’re pretty much guaranteed to have complete data integrity after the 30 year mark.
At that point, you can probably transfer all the data into your petascale holographic storage installed at the base of your skull.