We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
I think it is better than most other flash. In other words, no. It is not good for cold storage. But it is a very good flash memory for normal use. I have never lost any data stored on one.
There is nothing that is good for long term cold storage.
You need multiple copies on different types of media. Check/repair it regularly and migrate to new media every now and then. Every 3-5 years.
So just power it up and repair it every 6 months, and recopy it into the USBs every few years?
No. I don't think you should use USB Flash at all, except as part of daily use. For long term storage, up to a year, use a proper SSDs and/or HDDs. And check and migrate.