3 ms·

Over time, flash memory leaks the charge that holds your data. Here's an explanation I found: https://old.reddit.com/r/askscience/comments/5cexmj/how_stable_ar

• Rd6n6 5y ago
  > FLASH memory works by essentially placing some electrons on an insulated island of material through quantum tunnelling and then "trapping" them there. However, there is some probability that they can tunnel off, and thus the stored charge does leak out over time. How long it takes for enough charge to leak off that a "read" can't tell the difference (signal to noise wise) depend on the manufacturer and specifications but 10 years is definitely in the danger zone. There's also a stress degradation issue but that probably doesn't apply here. Thanks for the link!