I scan my actual paper-and-toner wallets, copy them to multiple encrypted microSD cards, hide them well in multiple offsite stashes, and then securely shred the original files and tear up the original printed wallets and flush them down the toilet.
Flash memory has limited data retention, have you taken precautions against this?
Only to the extent of checking them from time to time. If one were to fail, I'd replace it with a copy from one of the other.
Personally, I've never had an SD card or SSD fail and I was an early adopter of SSDs. I'd hate to admit what I paid for my first PATA 32GB Memorite SSD almost a decade ago but it's still running fine.
When OCZ brought out their first Vertex SATA SSDs, I replaced my Raptor RAID-0 array with 4 of them. When I got my first Revodrive PCIe RAID SSD card, the Vertex cards went into netbooks. All are still working as far AFAIK.
The only flash memory I've had fail were USB keys and that was probably due to physical abuse.
