So I took it upon myself to answer the question of “what are the best and cheapest microSD cards out there?” This includes evaluating whether they’re fake flash, how well they perform, and how many read/write cycles they can endure before they start failing. So far I’ve tested four to the point of failure, I have 37 being tested right now, and I have 21 more waiting to be tested.
Sorry for the horrendous cable management — I have cable ties on order.
Flash is... not great for cold storage from what I've read. Electrons eventually leak out and your data is gone. Well, unless you put it in freezer
Fun fact: JEDEC specification for commerical flash only specifies year of retention as minimum at 30C and much lower at elevated temperature
https://www.seagate.com/files/staticfiles/docs/pdf/whitepaper/tp618-ssd-tech-paper-us.pdf