They quote (statistical estimate) 1,000,000 hours! My experience wouls say that's not totally improbable, given the nimber of failures I've had over time, although I think I've only ever kept one for about 60,000 hours. That is pretty well permanently powered on in my case, low number of spinups, and kept fairly cool (either the microservers which are well cooled, or big Corsair cases).
We are well above the level of the building designated as the flood relief centre. The storage unit is a lot higher! Can't do much about the EMP; if it covers here and North Americ as well, I doubt I'll care!
I wondered that about DVD vs. CD, and they seem pretty well the same. The only CD failures I had were very cheap media (early days) and soem problems with discs for about 2 years 2004-2006. I have check read back to my oldest discs with no trouble in most cases, barring those which had systematic problems. It's clear (I keep logs of software updates) that one version of the writer software was glitching at the same point every time; I suspect a buffer underrun. I managed to recover it all one way and another as the glitch was in a metadata area. For the last two years, everything gets ECCs added.
And they ought to survive EMP too!