Originally Posted by Blameless
While the idea that an SSD will lose data in days if unplugged is a farce, they will still eventually lose data (especially if old), and far more quickly than HDDs.
Even a lightly used SSD, filled with archived data, will be mostly empty/corrupt if left in a box for ten years.
I can reasonably expect a mechanical HDD that has been stored in a moderately controlled environment to work and retain all of it's data if plugged in after 20 years (and I do have 20+ year old HDDs and other magnetic media) of sitting on a desk. The limiting factor is the integrity (rate of lubrication loss and corrosion mostly) of the spindle motor and a head actuators, the platters themselves will hold data for centuries, if not longer.
While HDD platters will hold data almost indefinitely, you hit the head on the nail when you pointed out that motors, head actuators, etc. will not. For long term static storage (no power applied), tape is still king but HDDs aren't far behind. Only some physical media, such as paper and stone tablets, have the potential to last longer. The chances are most media will be obsolete before it can lose data.
In my case (and, I suspect, most other people here), none of my data is truly static. All of it is (or soon will be) stored right on my computer and my multiple backup drives get powered up at least once every month (usually more often). I'm planning on going all SSD in the not too distant future and I'm not the least bit worried about my data going south since every drive, active and backup, will get powered up once a month which is far more frequent than required to prevent SSD from losing data due to decaying charge