Doesn’t thumbdrive data decay over time? Like all flash based storage types do
They are super cheap and fairly reliable but not quite reliable enough for backups.
It's an interesting idea to deep-freeze your drives, but the thermal stress from modern frost-free freezers that automatically dethaw periodically may negate the benefit of chilly bits...
If you don't have that much to store, and are worried about data durability, I'd suggest looking into M-disc instead.