All types of flash memory are a bad idea for long term storage. They discharge over time.
Discharged sd cards? Never heard about it!
SD cards are the safest digital storage, much more reliable than CDs or DVDs. But better create an additional paper wallet from your private key, then you're completely covered.
They need power every once in a while
Get these
http://www.newegg.com/Product/Product.aspx?Item=N82E16800995117You're right about the sd cards, only last a few years... did'nt know that!
M-Disks are great or you could take this:
http://www.sandisk.com/products/usb/memory-vault/Paper is still king. Stored properly in a cheap firesafe, paper will survive a house fire.
I also use M-disc, but I don't trust them yet. The concept seems very solid. The drives suck, I think I've got a 50% failure rate on the LG drives (of about 40 installed) in the first year, but that doesn't seem to be a problem for media lifetime. I also have a few media that have appear to have spontaneously grown what appears to be a thick dust layer despite storage in Tyvek sleeves, but they still read fine.
I have no idea about that memory vault. I note that the linked website doesn't give any indication of what it really is, or how it works. Appears to be just flash memory plus marketing. Assuming that they've solved the discharge problem (and I see no reason to believe that they have), you still have the problem that flash drives sometimes just die a sudden and mysterious death. Or am I the only one that occasionally plugs in a USB stick only to find that it has turned itself into a brick since the last time I used it?
