I hate to be a cynic on this one, but I never found micro SD cards reliable enough to store anything longer than absolutely neccessary. Usually that is until I can move the data to a better storage medium. The tech that runs on these devices is incredibly cursed, and keeps changing very fast.

30C3 had a fun talk about the internals of mSD cards.

https://media.ccc.de/v/30C3_-_5294_-_en_-_saal_1_-_201312291...