Or look for industrial / business grade stuff with long retention times. Old flash also means less sophisticated controllers etc

Watch out for flash data corruption. Lots of cheap flash (USB sticks, SD cards, SSDs) lose data after just a few years of offline storage. Something something quantum tunnel bullshit, iirc.

So either look for media that guarantee long cold storage retention (lots of businesses need to keep shit for 10 years for tax reasons), or occasionally plug it in and let do the housekeeping.